
Class LKvSjS 



Book, 



P4 



T 



GpightN? 



COPYRIGHT DEPOSIT. 



ELECTRICAL AIDS 
TO GREATER PRODUCTION 



ELECTRICAL AIDS 
TO GREATER PRODUCTION 

PLANS, METHODS AND APPLIANCES BY WHICH 
INDUSTRIAL ELECTRICAL ENGINEERS ARE 
MEETING INCREASED DEMANDS FOR POWER 



COMPILED AND EDITED BY 

ALLEN M. PERRY 

Engineering Editor, Electrical World 



First Edition 



8 ' ' 

- 



PUBLISHED BY 

ELECTRICAL WORLD 



McGRAW-HILL BOOK COMPANY, Inc. 

Sole Selling Agents 

239 WEST 39th STREET, NEW YORK 

1919 



*3 






6't» 



Copyright, 1919, by th 
McGRAW-HILL COMPANY, Inc. 



J^ 



JUN 23 1919 







CI.A525964 



o \ 



PREFACE 

Eighty per cent, of the power used in making munitions has 
to be applied electrically. The Great War has brought to the 
engineer in the industrial plant, to the chief electrician of such 
plants and to the consulting engineers at work in laying out and 
designing the electrical equipment for industrial work, many 
new opportunities. 

Emergency power needs have been supplied, additions and 
alterations to wiring systems to carry added loads, extensions 
have been built, all with the general idea of helping to increase 
factory output and hold down factory costs. 

The war indeed has emphasized the inherent economy and 
flexibility of electricity as a method of driving all classes of 
machinery and has stimulated greatly the application of 
electricity for lighting and power. 

This volume is written out of the experiences of the men 
who have been engaged in this work. Electrical World from 
week to week has presented articles on application of electricity 
to plants, taking up the problems of installation and mainte- 
nance as well as the problems of layout and control. 

In this volume, the best of this practice has been assembled 
to provide for the work of reconstruction now upon us a back- 
ground of practical suggestions to help install, operate and 
maintain electrical equipment in different classes of industries. 

The material has been chosen and edited, not to make a text 
book, but rather a practical handbook of methods, schemes and 
plans which can be lifted out and adapted to a wide variety of 
conditions. 

For the information presented, Electrical World is indebted 
to the cooperation of scores of electrical engineers in industrial 
establishments; where permitted, individual credit has been 
given to the men who together have met so successfully the 
problems of applied electricity during the war and whose work 
forms the basis for the practical application in factories to help 
increase output and reduce costs under the normal conditions of 
peace. 



CONTENTS 



PAGE 

Preface v 

Chapter I General Power Problems of Industrial 

Plants 1-46 

Chapter II Distribution, Transformation, Switching, 

and Protection 47-113 

Chapter III Motors, Control, Specific Applications, 

Troubles and Remedies 114-199 

Chapter IV Illumination — Selection of Equipment, 

Economies, and Specific Applications . 200-252 

Chapter V Electric Furnaces, Welding, Etc. . . . 253-290 

Chapter VI Meters and Measurements as Applied to 

Industries 291-299 

Chapter VII Handling Material in Industrial Plants 

with Electric Tractors 300-304 

Chapter VIII Outdoor Substations 305-323 

Index 325 



ELECTRICAL AIDS TO 
GREATER PRODUCTION 



CHAPTER I 

GENERAL POWER PROBLEMS OF 
INDUSTRIAL PLANTS 

INDUSTRIAL APPLICATIONS OF ELECTRICITY 

If it were possible to state in just one word what the great 
advantage is that has created the universal adaptation of elec- 
tricity to practically every known industry, it might be summed 
up in the one word "control," says Dwight D. Miller, formerly 
with the engineering department of the Society for Electrical 
Development, Inc. This is true since by means of control not 
only is the highest economy secured, but also increased produc- 
tion within a given time and of a quality higher than possible to 
attain by those other methods of power application in which the 
possible degree of control is only nominal by comparison. 

Notwithstanding the fact that the electrical industry had its 
inception in the production of light, still, owing to the limitation 
of space allowed, this subject must be passed over with the state- 
ment that there have been many and large increases in efficiency 
in the various lamps invented and manufactured from the time of 
the first open-arc lamp down to the highly efficient gas-filled 
tungsten-filament lamp of to-day. Up to recently the cost of 
lighting had steadily decreased, so that it is possible to obtain 
many times the candlepower for the same energy consumption, 
or the same candlepower at a greatly reduced cost for energy 
consumed. 

In dealing with the subject of heat, atmosphere, time and tem- 
perature are the three controlling and essential factors necessary 

l 



2 ELECTRICAL AIDS TO GREATER PRODUCTION 

for quality production in quantity, especially in those processes 
involving high temperatures. The fact that these three factors 
are more easily and accurately controlled through the medium 
of electric heat than is possible with any method of combustion 
heating makes it a heating medium so far superior to others as to 
offset in many instances its higher first cost. This is at once evi- 
dent when we recognize that heat produced from electric energy 
is produced at 100 per cent efficiency and is accomplished auto- 
matically under fixed conditions, beyond the effect of human 
errors consequent to manual control, while the utilization of the 
heat of combustion devices involves a large number of variables 
all of which either involve the human element in their control or 
are beyond its power to correct. The heat of electric energy is 
peculiar in that it can be generated in any quantity regardless of 
temperature. This feature is unique and renders its utilization 
much more flexible and its control nicer than is the case where 
the heat of combustion must be utilized. With given fixed elec- 
trical conditions, such as line voltage and resistance of the leads, 
electrodes and resistor material, the same amount of current will 
flow, automatically producing the same temperature to an exact 
degree, since it is governed by Ohm's law. AVith this law the 
human element has absolutely nothing to do, because as long as 
the voltage and resistance of the circuit remain constant the same 
current must flow per se. 

In general the ratio of efficiency of application of heat of 
combustion to application of electric heat becomes greatly in 
favor of the latter as the higher temperatures are reached, be- 
cause electric energy is always transformed into heat at 100 per 
cent efficiency, regardless of the temperature, so that only the 
heat losses due to radiation, conduction and convection must be 
taken care of. In the case of combustion heating, however, it is 
the lack of control of the factors producing the heat itself which 
prevents perfect combustion and, combined with the heat losses 
just mentioned, renders its efficiency of utilization much less. 
In fact, it is by no means rare to find coal or even oil-fired fur- 
naces to-day whose thermal efficiency is no greater than 1% per 
cent, which means that sixty-five times as much heat as is util- 
ized in the useful work of heating is discharged into the atmos- 
phere. 

Much has been said regarding the high cost of electric heat — 



GENERAL POWER PROBLEMS 3 

that it is much, more expensive than the various forms of fuel. 
This is true when viewed from a B.t.u. basis only. The crux of 
the whole matter, however, lies in the fact that the cost of heat 
energy alone, as compared with the entire cost of the finished 
product, is in many instances negligible. Many items enter into 
the total cost of production, of which heat energy is only one; 
so that, while electric heat may be more expensive, if by its use 
the other items (such as time required, labor, fire insurance, etc.) 
are cut in greater proportion, producing greater quantity as well 
as improved quality, it is evident that not only is electrically 
generated heat cheaper to use but also that its use is imperative 
in order to compete successfully with those using it in similar 
processes. 

Probably no more striking and forcible example of the saving 
of both- time and money effected by the use of electric heat can 
be found than in the case of repairing the interned German 
ships. Although there was a total of 109 ships damaged, which, 
if new cylinders and parts had had to be supplied, would have 
taken eighteen months to two years to repair, all these ships 
were placed in service in less than eight months by the use of 
electric welding. The estimated cost of repairs on the first ship 
amounted to $32,000, and the time required from ten to twelve 
months for completion. By means of electric welding the work 
was completed in fifty- two hours at a cost of less than $2,000 
for the actual work done. Moreover, the cylinders withstood a 
test of more than 50 per cent in excess of their normal working 
pressure, although it is customary to test them up to an excess 
pressure of only 20 per cent. In many cases an electrode high 
in manganese was used which in itself supplied the proper ten- 
sile strength to the weld. Thus repairs were easily made in 
places which would have been extremely difficult, if not entirely 
inaccessible, had a method of welding which required a flux been 
employed. 

Spot Welding Used Extensively. Another case in point is 
the manufacture of the all-metal automobile bodies by means 
of spot and arc welding. Indeed, were it not for the ease and 
rapidity with which welds are thus made, together with the 
strength obtained, many manufacturing processes which involve 
a complete and oil-tight junction of metals would be commer- 
cially impossible, the stock being too light and thin to permit of 



4 ELECTRICAL AIDS TO GREATER PRODUCTION 

riveting successfully. In manufacturing small articles like 
window-sash pulleys, as is done at the American Pulley Com- 
pany, Philadelphia, by spot and projection welding, many thou- 
sand welds are made per hour — in fact, just as fast as the oper- 
ator can press a lever, demonstrating in a most striking manner 
both the flexibility and ease of control of the electric welder. 
Ship plates are pinned to the frames of the vessel by spot weld- 
ing and later on are welded along the edges, practically fusing 
the plates into one another. In both of these applications heat 
is developed at the exact spot, to the exact degree and for the 
exact length of time only to effect a perfect junction of the 
metal. Where can you find a fuel-fired process so simple, so 
complete and so efficient in utilization of heat? 

The practice of heating by induction is rapidly coming into 
use. In this case the material to be heated forms the short- 
circuited secondary of the transformer by which it is inclosed. 
While this method of heating is probably the most efficient of all 
now in commercial use in its practical application, it can only 
be used in connection with materials of uniform cross-sections, 
because with an uneven cross-section part of the piece may be- 
come superheated or even burned before the other part attains 
the desired temperature. 

Industrial Heating. Lieut. Col. C. F. Hirshf eld, when head of 
the research department of the Detroit Edison Company, made 
some very interesting experiments with internal heating in con- 
nection with the baking of "japans." He says: "It is of par- 
ticular interest to note that baking by internal heating is essen- 
tially an electrical method, and that it is far removed in every 
way from methods previously in use." In his paper on "Low 
Temperature Electro-Thermal Processes" he clearly demon- 
strates, by means of micrographs, that the surface coats of ja- 
panned articles baked by the heat radiated from electrical air- 
type heaters possess a much higher and more perfect gloss or 
finish, that they are denser, freer from crater holes and will 
weather much longer than is the case with those baked by hot- 
air convection currents of combustion heating. Moreover, the 
time of bake was reduced to two hours and forty minutes for 
the electric compared with five hours and thirty minutes for the 
combustion method. 

He next experimented with inductive or internal heating as 



GENERAL POWER PROBLEMS 5 

against electrical radiation and found that better results could 
be obtained with a bake of fifteen minutes and at a temperature 
of 338 deg. Fahr. (170 deg. C.) by internal heating than could 
be secured by means of external electric heating (radiation) 
using a temperature of 446 deg. Fahr. (230 deg. C.) for forty- 
five minutes. He says : "It seems probable that one coat baked 
in this way will prove the equal of two or three baked by the 
older methods. The effect of all this upon energy charges for a 
given weight of metal baked is perfectly obvious." 

In view of the superior results noted above it is unfortunate 
that induction heating cannot be universally adapted to the 
baking of japanned articles. However, it is being successfully 
used in heating metal tires for wagons and rims for large auto- 
mobile trucks, since in these cases the cross-sectional area is 
uniform. It is also being tried out in connection with elec- 
trically heated boilers. In this case a hollow brass casting forms 
the short-circuited secondary of the transformer and heats the 
water as it flows through. The casting is connected to the boiler 
in a manner similar to a gas hot-water heater of the circulation 
type. 

By the use of automatic devices such as time elements with 
solenoid switches, etc., ovens can be automatically controlled and 
brought up to temperature before the operator arrives in the 
morning, so that there is no time lost in starting the day's work, 
or the bake may be completed and power shut off after the 
quitting time of the operator at night. 

Many other examples can be given showing the advantages of 
electric heat in low-temperature processes, such as its use in 
connection with linotype melting pots, glue pots and hot tables 
of various kinds. Here the heating units are small, compact 
and easily so adjusted that heat is applied exactly in the location 
desired and accurately controlled either manually or auto- 
matically by the many devices already perfected for this pur- 
pose. 

Electric Furnaces. Through the medium of the various elec- 
tric furnaces now being rapidly installed by progressive com- 
panies, the entire metallurgical industry is much benefited. By 
the use of the electric arc the temperature range above zero has 
been practically doubled and made available for commercial 
uses. This has not only opened up a wide field for development 



6 ELECTRICAL AIDS TO GREATER PRODUCTION 

in the electrochemical industry but has also already resulted in 
the commercial production of materials heretofore unobtainable 
or previously unknown, such as aluminum, calcium-carbide, car- 
borundum and artificial graphite. 

On account of the great heat developed in the electric furnace, 
reactions take less time and are more complete, hence the yield 
for a given time is increased. Because of the fact that the heat 
of the electric furnace is not dependent upon combustion, and 
can be used in a neutral or reducing atmosphere, it is a "clean 
heat, ' ' in that it is not contaminated by the various products of 
combustion. Thus both the time lost and the expense incurred 
in using deoxidizing agents are, to a great extent, done away 
with and the product is of a higher quality. 

Not only has the electric furnace made tremendous strides 
within the past ten years in the steel industry both in connec- 
tion with the melting and refining of steel and in its heat treat- 
ment, but it is now rapidly establishing itself in that other great 
allied branch — the non-ferrous field. 

Many books have been written and the technical press for the 
last three or four years has contained a multitude of articles on 
the advantages of the electric furnace. Briefly, the whole sub- 
ject may be summed up by saying that the use of the electric 
furnace enables commercial practice to approach very nearly 
the scientific accuracy of the laboratory, thus insuring not only 
certainty of production and duplication of results, but also pro- 
duction of a quality higher than can be commercially obtained 
by the use of combustion heating. 



THE POWER PROBLEM OF THE MANUFACTURING 

PLANTS 

Although power is an important factor in production, it re- 
ceives very little consideration compared with other factors, 
points out Sydney Fisher, an electrical engineer who has been 
connected with large manufacturing companies in England and 
with two major war industries in this country. Power must be 
available in sufficient quantity when required, and its supply 
must be unfailing. Production must never be held up for 
power; in other words, power must be ever ready for produc- 
tion. These exacting requirements can be met in modern plants 



GENERAL POWER PROBLEMS 7 

with electric service, and yet the cost of this vitally important 
factor in production does not amount, in many cases, to more 
than a few mills per unit of product. This has been made pos- 
sible by the remarkable development of electrically operated 
equipment in late years. 

Not only in the supply of motive power and power for light- 
ing has electricity simplified production, but also in its applica- 
tion to production processes. Temperature control, so impor- 
tant in delicate heat-treatment operations, is a reality, and 
losses due to radiation, etc., are very small. The electric weld- 
ing machine is used not only for welding, where it has elimi- 
nated many operations, but also in delicate heat-treatment opera- 
tions where high local heating is required. It is also used in 
heating and clinching rivets, these operations being performed 
together. Electric plating and cleaning baths have greatly sim- 
plified operations which heretofore were difficult and expensive. 
The battery truck has made rapid transportation over short 
distances possible with economy in time and help. Scientific 
heat treatment has been made possible by the development of 
the thermo-electric couple for pyrometry. The telephone, the 
telecall, the fire alarm, all play a very important part in plant 
operation. 

Efficient Operation and Reliable Service Chief Considera- 
tions. Reliable equipment is only one part of the problem, 
however — a very important part, to be sure, but not the all- 
important part. Enough power and continuity of service form 
the prime consideration of the power engineer, but over-equipment 
in any part of the system will result in poor operation and 
unreliability when the plant is in full swing. Efficiency and 
continuity of service can only be obtained through scientific 
selection and arrangement, careful installation and operation, 
and proper maintenance of scientifically designed reliable equip- 
ment. 

The following suggestions, based on two years' experience in 
power work at one of the largest munition plants in this country, 
if not the largest, may be helpful to those engaged in present 
and future power work. Suggestions will be offered under the 
following headings: (1) organization, (2) selection of equip- 
ment, (3) inspection, (4) installation, (5) operation, and (6) 
maintenance. 



8 ELECTRICAL AIDS TO GREATER PRODUCTION 

The power engineer and the production engineer of a muni- 
tion plant, or, in fact, any manufacturing plant, should each 
be responsible to the chief engineer. On no account should the 
power engineer be responsible to the production engineer. The 
production enginer is always afraid of an insufficiency of power. 
If allowed to have his way, complications will ensue. 

Selection of Equipment. Generating equipment rated at 
2300 volts, three-phase, 60-cycle, with 440-volt power and 110- 
volt lighting equipment, is without question the best system for 
industrial plants, in the writer's opinion. This is true from the 
initial-cost, operating and maintenance standpoints. The selec- 
tion of generating, controlling, transmission, transforming and 
distributing equipment should be based on the assumption that 
a high motor load factor (90 per cent) will be maintained where 
possible and that the necessary synchronous apparatus will be 
installed at the load to bring the power factor up to 80 per cent 
at the transformer stations. This will result in the correct 
design of all branches of the system, insure subsequent efficient 
operation, reduce the possibility of breakdown to a minimum 
and reduce the cost of equipment. 

Careful selection of motor equipment can be made without a 
large expenditure of time and money. Elaborate test equip- 
ment is not necessary. A young electrician carefully instructed 
and provided with several ammeters (0-15 amp., 0-75 amp. and 
0-150 amp.) and with a suitable voltmeter can do all that is 
necessary. Records should be made of the minimum, average 
and maximum currents and the order and frequency of their 
occurrence. All peculiarities of the work cycle can be expressed 
in terms of current. The corresponding power output values 
can be obtained from a current-horsepower output curve plotted 
from manufacturer's data on efficiency and power factor at 
various loads. 

The rated output of the motor should equal the average load 
demand. Peak loads not exceeding 150 per cent rated load and 
occurring at intervals for short periods may be taken as an 
overload. This apportionment of motor to load will insure a 
power factor of 80 per cent. The first two or three motors will 
have to be selected by well-based guesses. After tests have been 
made on these units the results can be used in making more 
scientific selections of the other units. At the plant on which 



GENERAL POWER PROBLEMS 9 

the writer bases most of his opinions 400 motors aggregating 
6000 brake-hp. were selected in this way. Careful study of the 
work cycle often results in the coupling of two drives on one 
motor with resulting adequate power for each and a high motor 
load factor. 

When the load is intermittent and fluctuates, as in the case 
of drop hammer and heavy press drives, a high average load and 
consequent high power factor is unobtainable. In such cases 
use should be made of a synchronous motor fan or blower drive 
requiring sufficient reactive power to raise the power factor 
to 80 per cent. Where possible reactive power should be sup- 
plied at the load, thus increasing the generator, transmission- 
line and transformer capacity for useful average power and 
reducing equipment and transmission losses. The 2000-kw. 
turbo-generator unit is a good unit for industrial plants. 
Where the space is not too limited two such units are advisable, 
one of the bleeder type and the other of the mixed-pressure 
type, as they make the best use of low-pressure steam during 
winter and summer months respectively. 

Control apparatus is pretty well standardized. In addition 
to standard exciter, generator and feeder panels, a station re- 
cording voltmeter, a power-factor meter, a voltage regulator and 
a ground detector (three-phase) will be found necessary. 
Power-limiting reactances are not a necessity even with time- 
limit relays, as the reactance of modern generators is sufficient 
to limit the current of the usual short circuit. 

Combined turbine, motor-driven exciters are to be recom- 
mended for munition plants. Under normal conditions of 
operation the exciter is motor-driven. Should the speed of the 
motor drop below 95 per cent synchronous speed, the turbine 
automatically takes the load. This insures sufficient power for 
the station lighting in the event of a shut-down. 

Fiber duct gives very good results for underground transmis- 
sion. Manholes should not have perforated covers, should be 
shaped to the lay of the cable and should be made thoroughly 
waterproof. Should a circuit pass near furnaces or heated area, 
it should be run through a tunnel opening into a well-ventilated 
manhole at each end. Overhead transmission is less expensive 
and quickly installed but is easily tampered with. 

Value of Several Motors to Each Machinery Group. Motor 



10 ELECTRICAL AIDS TO GREATER PRODUCTION 

equipment should be selected on the basis of two or more to 
each group of machinery. This arrangement is more expensive, 
but is preferable for several reasons. For instance, a high 
motor-load factor is more easily obtained, a 42-hp. average load 
being better supplied by three 15-hp. motors, or one 20-hp. and 
one 25-hp. unit, than by one 50-hp. motor. Obviously when 
power requirements are uncertain and quick deliveries of small 
sizes are possible, a number of smaller sizes is better than a few 
large sizes. Furthermore, if the motor equipment is reduced to 
a few standard sizes (5 hp., 10 hp., 15 hp., 20 hp. and 25 hp.) 
fewer " spares" are required and the expense is less, the units 
being smaller. 

With this arrangement, if many machines are idle or the duty 
is light, whole sections can be run on one of the motors, the 
others being disconnected. Another advantage of this arrange- 
ment, especially in a plant just being built or extended, is that 
operation does not have to be delayed by deliveries of equip- 
ment. If the generator capacity is small owing to slow deliv- 
ery of units, loading up one motor in the section instead of 
having two or three running lightly loaded will relieve the sta- 
tion units of unnecessary reactive power load and hence in- 
crease the station capacity for the average power load. In the 
writer's experience a 20-hp. motor has taken the load of an 
entire group (33 hp.) for two hours, with the aid of an ordinary 
desk fan to keep it cool, while another motor in the section was 
being replaced. This is another reason why there should be 
more than one motor driving the group. 

Money spent on circuit breakers to isolate circuits is by no 
means wasted. A short circuit at some remote point will shut 
down an entire feeder, perhaps the plant, unless some precau- 
tionary measure is taken. Overload relays are not desirable on 
individual motor circuits, however, unless steps are taken to 
study the work cycle and set them for the maximum current. 
Furthermore, they also must be inspected frequently, otherwise 
they will trip and shut down a group of machines, causing un- 
necessary delay. If a motor is carefully selected and fused for 
the maximum current, there should be no trouble. A 440-volt 
circuit is advisable for motor applications, as the copper for a 
220-volt circuit is expensive. 

In the opinion of the writer the incandescent lamp is best for 



GENERAL POWER PROBLEMS 11 

lighting, 60-watt and 100-watt units providing general illumina- 
tion being preferable for production work and 25-watt or 60- 
watt individual lamps for tool and assembly work. Vapor 
lamps, while they possess advantages as regards quality of light, 
are easily damaged and the maintenance is high. 

Inspection and Installation of Equipment. Standard appa- 
ratus, such as motors, transformers, control equipment, etc., as 
supplied by reliable firms, are carefully inspected at the shop. 
Frequently, however, machines built to supply a less urgent 
order are supplied, and while they may be identical in design, 
they have different characteristics. In the writer's experience, 
three exciters specified for parallel operation were subsequently 
found to be over-compounded, flat-compounded and under-com- 
pounded respectively. The adjustment could have been made 
very easily at the shop but involved considerable time and ex- 
pense after installation. 

Tests for grounds in the fields of generators should be con- 
ducted. If the system is installed on contract, the layouts 
should be studied carefully and the sizes of bus copper and 
cable from generator through to motor should be checked. It 
is surprising how errors creep into a mass of detail. Occa- 
sionally 300-kva. transformers may be accidentally installed for 
500-kva. service and the error not detected until the plant 
is in "full swing"; then the tar begins to drop and the bus 
copper changes color. Contacts of circuit breakers should be 
inspected with a thickness gage to detect poor contacts before 
they cause trouble. 

While cable purchased from a reliable firm is guaranteed for 
a year, the reels should be meggered before and after being 
drawn through ducts. A megger test set is expensive, but it 
will be found invaluable in locating defects and ascertaining the 
condition of equipment. Transformer taps should be carefully 
checked, as phase reversal may cause considerable trouble when 
two transformer houses are tied together. While awaiting in- 
stallation do not allow transformers to remain in the rain un- 
covered. The air gap and oil rings of motors should be in- 
spected and the rotor should be tested to see if it binds. Com- 
pensator contacts should be inspected, as three-phase starting 
and single-phase running, due to a bad contact on the running 
side, is by no means uncommon. 



12 ELECTRICAL AIDS TO GREATER PRODUCTION 

The installation of generating, transmission and transform- 
ing equipment is usually and preferably placed in the hands of 
contractors. Curves showing daily progress in all branches of 
work should be plotted on one sheet and the contractor con- 
sulted to ascertain the cause of delay in any branch of the work. 
Installation should be constantly checked from drawings as 
defects do not come to light until the plant is in full operation, 
by which time the bills may be paid. 

The power engineer should consult with the machinery lay- 
out department to determine the best grouping of machines from 
a power standpoint, and to eliminate short double-cross belts 
where possible and the arrangements which require excessive 
starting currents and needless constant expenditure of energy 
in overcoming friction. Sometimes chain drives are advisable, as 
they will transmit overloads. Motors are frequently regarded 
as underrated because the main drive of a belt, particularly on 
a damp day, is very inefficient. Excessive belt tension is fre- 
quently the cause of a seized motor bearing. A. motor should 
be given a central position relative to the group of machines 
which it is required to drive, and the motor pulley placed under 
a girder if possible. 

Operation of Equipment. Instruction cards should cover the 
operation and maintenance of every piece of equipment in the 
plant. No doubt should be left in the mind of the operator. 
Rules for starting, stopping and oiling should be very complete. 
Rules giving the method of procedure in case of shut-down can 
be drawn up to cover nearly every possible condition. A com- 
plete set of instruction cards will prevent shut-down, shorten 
the period of shut-down and place responsibility on the right 
person. A comprehensive set of signals (whistles and colored 
lights) should be in operation in the station, covering the start- 
ing and stopping of the main units and auxiliary apparatus. 

Voltage regulators are a boon, but they fail sometimes. They 
may operate satisfactorily twenty-four hours a day for six 
months and then fail, causing the station to lose the load. Once 
in six months is once too often when a 10,000-hp. load is dropped 
and about 25,000 men are forced to be idle. At the plant where 
the writer is engaged periodic shut-downs were experienced 
until the regulator was made semi-automatic. If the regulator 



GENERAL POWER PROBLEMS 13 

fails as now adjusted, the station voltage drops only to a certain 
value, which insures against dropping the load. This is done 
at a sacrifice of the automatic feature whereby the voltage is 
maintained constant under all conditions of load ; hence the 
operator must adjust the generator and exciter fields when the 
load "goes off" and "comes on" at recess periods to keep the 
regulator on the line. 

The field excitation of each generator should be adjusted so 
as to maintain the same power factor in each unit, as under this 
condition the station capacity will be a maximum. In 'some 
cases machines operate better at a lower or higher power factor. 
Sometimes it is desirable to raise the average power load of a 
bleeder turbine in order to obtain as much low-pressure steam 
as possible. Another precaution to take is to keep tie switches 
open when it is not necessary to have them closed, as the fuse 
capacity is doubled and the damage due to short circuits is 
thereby increased when they are closed. 

Operators should be instructed to start motors with quick 
decisive motion. "Hobbing" should be discouraged, especially 
when belts are being put on. If the proper compensator taps 
are used, the acceleration will be such as to permit applying any 
belt without danger to the operator. 

Where there are several motors on a floor one man should be 
detailed to start all of them so excessive starting current will 
be avoided. In addition, the man on the first floor should be 
instructed to begin starting motors at ten minutes before the 
starting time, the man on the second floor at eight minutes be- 
fore, etc. Where the plant is all on one floor the same effect 
can be produced by starting the departments in succession with 
small intervals between. The station switchboard operator 
should be notified when synchronous motors are either started 
or stopped, as reactive power load suddenly thrown on the sta- 
tion may cause trouble. 

Maintenance of Equipment. Maintenance men should be 
assigned to inspection when not employed in actual breakdown 
service. The importance of adequate inspection cannot be over- 
emphasized. Systematic inspection brings defects to light be- 
fore they reach the danger point. 

Ground detectors should be installed in the generator field 



14 ELECTRICAL AIDS TO GREATER PRODUCTION 

circuits and a three-phase ground detector in the main circuit. 
The station equipment should undergo a thorough inspection at 
short intervals which should include the inspection of oil-switch 
contacts and the timing of relays. 

Duct lines should be inspected frequently, at which time man- 
hole conditions should be observed and cables tested with a 
megger. Every feeder should be tagged in every manhole with 
a waterproof label. In addition there should be a diagram of 
each manhole showing the position of each feeder. A cable test 
set is not expensive and will be found very useful not only for 
locating grounds or other defects in cable but also for deter- 
mining resistances all over the plant — magnetic chuck repair, 
pyrometric work, telephone work, etc. 

Transformer houses should be roomy, well lighted, well ven- 
tilated and clean. The cause of water condensation anywhere 
should be investigated immediately. Transformer oil should 
be tested for water content at frequent intervals. 

Motor inspection should be very thorough. Slip rings should 
be inspected for pitting and oil rings should be tested to see 
that they turn. More motors shut down because of seized bear- 
ings owing to the lack of oil and also to stationary oil rings than 
from any other cause. The adjustment of overload relays and 
circuit breakers at frequent intervals should also be checked 
periodically. Compensator contacts should be inspected and 
replaced when badly burned. When a motor has the appear- 
ance of being heavily overloaded, a search should be made for 
bad contacts on the running side of the compensator. The 
maintenance of compensators is usually very high but can be 
reduced by careful instruction regarding the proper method of 
starting and by systematic inspection. 

The power engineer and his assistants, even though well or- 
ganized and well fortified with departmental rules and com- 
prehensive instruction cards, would do well to leave the office 
and stroll through the plant quite frequently. The power engi- 
neer should trust his assistants to the point of supporting them 
in a controversy. Furthermore, he should be safe in handing 
a problem to an assistant and then forgetting about it until the 
latter makes his report. However, a power engineer should not 
be too free in delegating responsibility to assistants. 



GENERAL POWER PROBLEMS 15 

LOW OVER-ALL COST AND CONTINUOUS 
PRODUCTION 

Refinements hitherto unthought of in industrial engineering 
are becoming more and more justified to-day as material and 
labor costs continue to rise because of the abnormal conditions. 
Maximum output is paramount, but coupled with it are the 
prime requisites of lowest over-all costs and continuous produc- 
tive facility. These spell economy; in fact, that word has be- 
come a slogan of the day. Inasmuch as induction motors play 
an all-important part in our industries to-day, some methods of 
purchase and installation will be given that have been suggested 
by A. P. Lewis, who was formerly electrical engineer of a large 
industrial plant in the middle West. 

Thing's to Consider in Purchasing Motors. It will be ob- 
served at a glance that the scheme hereinafter described applies 
principally to the large users, but its adoption by engineers of 
the smaller plants will result in greater over-all economy of 
operation, though in a smaller way. 

Certain assumptions will be made, in order to draw conclu- 
sions therefrom, and these can be varied to suit plants with any 
other status than that here considered. It will be taken for 
granted that it has been found advantageous to have a yearly 
contract for the purchase of motors, first, to benefit by a reduc- 
tion in the price thereby given, and second, because the manu- 
facturers will, under contract, hold for subsequent orders a 
small stock of motors in recurrent sizes — both features which are 
highly desirable to-day. 

The next step in the usual procedure would be to get prices, 
characteristics, etc. ; weigh one against the other and close the 
business with the logical manufacturer. This method will not, 
however, result in obtaining motors sure to fill requirements 
peculiar to existing conditions. So the commercial side of the 
problem will be passed by, for the minute, and the behavior of 
the apparatus already in use will be investigated. 

In the electrical engineer's office of the plant involved access 
can be had to his "motor repair record," a card index giving 
the repairs required on each motor in the plant and extending 
over a period of years. The assembly of this data might be 
made as shown in Table I. This shows at a glance in the 



16 ELECTRICAL AIDS TO GREATER PRODUCTION 



TABLE I— SUMMARY OF MOTOR REPAIR REPORTS 
Period January, 1916, to January, 1918, Xumber of Motors in Use About 

850 













Warn- 










Low 


Shorted Open 


Re- 


Out 




Open 


Loose 


Miscel- 


Bearing Dii 


•tv 


Coils 


Rotor 


wound 


Shaft 


Grounded Stator 


Rotor 


laneous 


120 ] 


L2 


1 




11 


5 




. . . . 








4 36 




















1 




25 




3 














3 




1 


20 


1 
3 














3 










9 










.... 


1 




2 


1 






8 










1 






. . 




. . 




5 






.... 
















.... 


3 


5 


133 4 


is 


29 


21 


19 


14 


8 


5 


3 


5 


Per Cent : 




















47 ] 


L7 


10 


7 


6 


5 


3 


2 


1 


2 



hypothetical plant of 800-odd motors where trouble is occurring 
in the motors and the proportion of each kind. A study of this 
record, which is an excellent criterion of future trouble, should 
certainly enable one to dissect a motor and see what particular 
manufacturer is turning out a machine which will reduce repairs 
to a minimum. 

Fundamentally, the induction motor may be divided into its 
mechanical and electrical characteristics, the former, in this 
discussion, to include both mechanical repairs and those inci- 
dental to insulation trouble, and the latter only the value of 
electrical design. By a rather extended operation considering 
capital investment, cost of power, etc., an approximate figure 
can be obtained for the latter which permits the assumption that 
the values of these two divisions stand in the ratio of 90 per 
cent and 10 per cent. 

Proceeding further with the subdivision of these two consid- 
erations, a final percentage weight list may be made up and 
percentages assigned as shown in Table II, column A. This 
column is arrived at by reference to the "repair record" and 
also by consideration of local plant requirements, such as diffi- 
culty of belt drives, dirty surroundings, vapors or acids present, 
any established dut/y cycle affecting temperature rating, starting 
conditions, value of power factor or efficiency predominant, etc. 



GENERAL POWER PROBLEMS 17 

TABLE II— PERCENTAGE WEIGHTS OF MOTOR CHARACTERISTICS 
WITH MANUFACTURER'S RATINGS 

Item A— B— C— D— E— 
I mechanical; total, 90 per cent. 

a. End bells; total, 52 per cent. 

1. Bushing construction, rings, 

etc 12 12 

2. Oil well, cover, etc 10 10 

3. Alignment, how made and re- 

tained 7 6 

4. Holding bolts, size and num- 

ber 5 5 

5. Size and rigidity 5 5 

6. Weight 3 3 

7. Design for dust prevention... 10 9 

b. Stator; total, 26 per cent. 

1. Material and construction.... 3 3.0 

2. Iron, how held 1 1.0 

3. Ventilation methods 4 4.0 

4. Open or closed slot 3 3.5 

5. If open bridge, construction. . . 2 2.0 

6. Cell insulation 4 3.5 

7. Coil insulation 5 5 

8. Phase insulation 3 3 

9. Terminal block 1 0.5 

c. Rotor; total, 12 per cent. 

1. Shaft size in bearings 

2. Bearing size 7 7 6.5 5 6.0 

3. Bearings, center to center 

4. Rotor insulation 2 1.5 

5. Air gap, in inches 0.5 0.5 

6. End-ring construction 2 1.5 

7. Attachment of iron to spider. ... 

8. Attachment of spider to shaft 0.5 0.5 0.4 0.35 0.35 

II. electrical; total 10 per cent. 

a. Power factors 4 4 3.5 3.5 3.0 

b. Efficiencies 3 3 3.5 3.5 4.0 

c. Temperature rise on test: 

1. 75 per cent load 

2. 100 per cent load 3 3 2.5 2.0 3.0 

3. 125 per cent load, two hours. ... 



10 


9.5 


11 


9.5 


9 


10 


7 


6.5 


6.5 


5 


4.5 


' 3 


4.5 


4.5 


4 


2.5 


2.5 


2 


10 


8.5 


8 


30 


2.5 


2.5 


1.0 


1.0 


1.0 


3.5 


3.5 


4.0 


4.0 


4.0 


3.0 


2.0 


1.5 


1.0 


4 


3.5 


3.0 


4.5 


5 


4.0 


0.0 


0.0 


3.0 


1.0 


0.0 


1.0 



1.25 


1.25 


2 


0.5 


0.4 


0.35 


2.0 


1.75 


1.75 



Total 100 96.5 91.65 83.75 87.45 

Other points may be more important in certain plants. For 
the purpose of this discussion a plant will be considered with 
the following features desired or present. Continuity of opera- 
tion (essential), cost of power low, a rebate given on purchased 
power for good power factor, dirt present in surroundings with 



18 ELECTRICAL AIDS TO GREATER PRODUCTION 

high, specific heat and causing a cutting action on bearings, dif- 
ficult belt drives, variable load characteristics but no duty cycle, 
overload capacity necessary and severe starting duty. 

The next step is to obtain complete data, from the manufac- 
turers to be considered, on a line of motors within the ranges 
considered, with stock samples of several sizes. By inspection, 
averaging dimensions, weights and characteristics, each item of 
the competitive makes can have assigned to it its relative por- 
tion of the whole percentage of the item considered. For ex- 
ample, as bearing bushing construction carries a value of 12 per 
cent, the manufacturer whose design is best, all things consid- 
ered, obtains full 12 per cent. The others fall below in direct 
ratio as determined by careful study. Proceeding in this way 
with all items and totaling each manufacturer's column, a result 
will be obtained which should show, all things considered, the 
motors which fill the requirements best. 

The cost of the machines has been intentionally left out of 
the tabulation, because the difference in price of standard motors 
to-day is small in comparison with repair expense, which may 
be of the order of 50 per cent of the first cost. Engineers may 
well insist in this case that over-all economy is established by the 
reductions of repairs, particularly where it is considered that a 
repair charge on a motor costing less money than another could 
be taken as a carrying charge on the higher-priced machine. 
For example, if the repairs, as shown in the record (Table I), 
cost $7,500, and these could have been reduced 50 per cent by 
paying $20 apiece more for the motors and obtaining a better 
design, it is evident that there would be available $3,775 to 
cover interest charges on the extra investment of $17,000. At 
current interest rates the extra investment would have earned 
roughly 15 per cent. These figures are not exact and only exem- 
plify the possibility of saving considerable amounts by judi- 
ciously purchasing motors to fill a required service. 

Installation and Maintenance. Certain fundamentals should 
be specially recognized in making motor installations — namely, 
that their life is determined by two things, bearing and insula- 
tion deterioration. Low bearings are usually caused by tight 
belts, dirt cutting the bushing or obstructing the proper flow of 
the lubricant, and vibration resulting from improper design of 
gear drives. Insulation deterioration may result from several 



GENERAL POWER PROBLEMS 19 

causes — overloading with resultant heat, dirty ventilating ducts 
restricting heat dissipation, chemical action on insulation result- 
ing from oil seepage or presence of harmful vapors, and precipi- 
tation of actual conducting dust in and around coils. The elimi- 
nation of these or similar causes cannot but reduce repair costs. 

Tight belts should be avoided by installing drives with long 
centers and by furnishing millwrights with the necessary instru- 
ments, tools and tables of tensions to fill any probable require- 
ment and then insisting on their intelligent use. Dirty bearings 
and oil wells are the most common source of trouble. Frequent 
inspections and periodical washings with gasoline help. Engi- 
neers should insist on carefully designed dust rings, oil-well caps 
which cannot be removed and which close by gravity, and should 
consider the use of ball bearings, which practically remove the 
chance for catching dirt and require only repacking in grease 
every few months or so. 

Vibration on gear drives is always present in greater or less 
degree. Its transmission to the bearings of induction motors 
can result in nothing but trouble. A machine driving through 
gears should be installed on as solid a base as possible and then 
have interposed a flexible coupling between it and the pinion 
shaft. Engineers who make the statements that their gear 
drives with pinions on motor shafts are satisfactory lose sight 
of the fact that the statement is a comparative one and that often 
a satisfactory drive can be made more satisfactory by the use of 
a flexible coupling at these points. 

Insulation deterioration from overloading can be prevented 
only by the proper use of fuses or relays and more particularly 
by a careful study of the load characteristics. If insulation is 
failing because of dirt lodging in the air ducts and a conse- 
quent retention of heat, dust-proof or inclosed motors may be 
the solution of the trouble. 

They may cost 30 per cent more than open motors, but one 
repair against the open motor may make up the difference, to 
say nothing of the cost of continual inspection required on the 
open motor to keep its ventilating ducts in proper condition. 
Vapors present in the air may also require the use of motors 
depending on radiation rather than convection for heat dissi- 
pation. 

A common source of insulation failure results from the im- 



20 ELECTRICAL AIDS TO GREATER PRODUCTION 

proper oiling of bearings, the well being* filled above the shaft 
clearance, whereupon it runs down the end bell and ultimately 
works into the winding. An overflow should be provided well 
below this point and the oiler equipped with a pump filler of 
which the nose can enter the well cover and the body be placed 
below to catch the discharge from the overflow pipe. In this 
way the well can be filled with no loss and the oil running out 
used again if it is in proper condition. At least it cannot get 
into the windings. In machine shops the writer has found a 
dust precipitation, consisting of iron particles and oil, in open 



Saae Plate, Da^a ( Hanuf ac turer. 0jL*vuJ<. ^Lt 


Cwi 
Freq. Phase S"S"o 


tor's Ho. t %j\ 


J Serial Ho. 1S7SI.0 Volta 
(Type Form eto. M 


to i 


Bate Purchased *|,lX|t Prloe ^\S^- 


Installation Order 2i + tJ " *** 


aovsjs>z;3 


Jfter*aB/? Hoi a»«*Sfc-K 

'.VlrlnffB/P Ho. nt"!*,!,, 
Controller Ko. 3 •♦•-»- 
lest Ho. 7 ft 


From 


To 


Late 


Remarks 


Hill 


Floor 


Dept. 


r.ili 


Floor 


Dept. 






Zj 


I 


3>I«S 




3 


Z. 


*<s n ( /; 






Card- 
Repair Parts Ho. 


Bearing fffi* 


SUtor Colls 1,^,,, 


Aotor Colls 154 


Jsrushes 1 £7 












Fig 


. 1— 


-Moto 


r Record 





motors that will actually break down on 440 volts with con- 
ducting points an inch apart. The residue is evidently dust as 
no gritty feeling is noticed. Inclosed motors are the remedy 
for this persistent trouble. 

Intelligent inspection is the surest way to prevent failures in 
induction motors. The number and kind of inspections, of 
course, depend on local conditions. The inspectors should, how- 
ever, be equipped with certain necessary data and should have 
considerable mechanical experience. A table of proper fuse 
ratings or overload settings, air-gap feelers or gages and bear- 
ing feelers should be provided. Their proper use anticipates 
trouble and allows adjustment before production is curtailed. 
The inspector should also be provided with means for taking oil 
samples and, if necessary, renewing oil in poor condition. Insu- 



GENERAL POWER PROBLEMS 



21 



lation resistance readings are desirable at frequent periods ; com- 
plete rewinding may be avoided where this resistance is low by 
carefully washing the insulation in gasoline, drying in a vacuum 
and impregnating with an insulating varnish. The repair rec- 
ord previously referred to in this article should serve as a guide 



aimer's lo. 



ESS? RECOED 
Card So. 



_iIaohi©es Drive n l-<ctujn/ 



a 



BO. of taohlnes ' &-*-t- 



imount of Shafting 



A^ctvm. 



Dat a 9> | K ) t 4 M aine of Teste r •Vk^S^JCCT 
Tenp. of Eooq__Sil-— ? Is t^s dorsal ? rXM^ , 



leap, of Llotor. 



< Is this normal?. 



<fu 



Operating Conditions .Dirt Vibration Oil Seepage, etc- ,p 

Stator ,Eotor 
Insulation Eesistance or or . . •■■?- 



Pwid 

:ic-load TEST 



iXQ 



Idle v/ith what__ 
Vl 72- 



Wi 



Jfc 



Total W 



P.F. 



L0A3 TEST (over l/2 hr. Period! 



What ftinnin^_ 
V] v 2 



*3- 



w, 



Total \V_ 



, I 2 

P.F._ 



0TE2E C0KDITI01S 



What Eunning_ 



Total T; 



P.F. 



Hoc ocmendat ions and EeaarJss. 



L— 



Fig. 2 — Test Eecokd 



showing what to look out for and inspections be directed accord- 
ingly, experience dictating the number and kind, together with 
desirable notations to be kept. 

Properly kept motor records are a valuable asset to the engi- 
neer responsible for maintenance as well as statistical reports, 
etc. With properly kept records available, he is at once aware 



22 ELECTRICAL AIDS TO GREATER PRODUCTION 

of the investment involved therein, the number and size of 
motors in the plant, the stock available for emergency nse, the 
connected horsepower by department, bnilding or floor, and has 
therein a ready reference for determining any repair parts re- 
quired as well as the tabulated load characteristics of motors in 
operation. 



STARTING AND CONTROLLING DEVICE Card No, 



3VX 



Desc 



I?- 
Data S 

Date. Purchased \ ' jtlli. 



Manufacturer's Data Sx^la^."Ho 3S (?7 %M 

Cost /0 "" 



Repair Parte 


Card No. 


Fiv^y/v* 


"?t"7 


-Cv*\cfco*3 


-7lf 



Fig. 3 — Starting and Controlling Device Record 



Five form cards are all that is necessary to file these data and 
to have as elaborate a cross index at hand as is necessary in the 
average plant. Fig. 1 shows a preferred form of motor record 
card, which is filled in as far as possible at the time the motor 



REPAIR PART 



Card No. I^tf 



Description 

Manufacture] 






Manufacturer' 8 Identification 




•*-*lb3nS 



jtt 



Ltot^C^uNo B13 ISH-iw 



Fig. 4— Repair-part Record 

is purchased, additional information being entered as it becomes 
available after receipt of motor and its installation. The vari- 
ous headings and items on this card need no elaboration. On 
the reverse side thereof is the repair record of the particular 
machine, which shows the date, kind and cause of the trouble 



GENERAL POWER PROBLEMS 



23 



and identifying means for determining the cost, such as the 
order number. This form (Fig. 1) refers to three other forms — 
the test card (Fig. 2), the control card (Fig. 3), and the repair- 
part card (Fig. 4). 

The test card contains such data as are necessary to study 
intelligently the load characteristics of the motor in question. 
On the reverse side of this card is a brief description of the 
method of drive together with pulley or gear sizes. The con- 
trol card describes the starting or controlling device of the 
motor, with repair parts for it, and with space on the reverse 



Owner's No. '^ ' 



Horse Power _ 
Speed %SQ 



IS" 



Manufacturer 



fto, 



T-vne. fAO A.C. 

Voltage S3*Q Freq. _f£. 

Serial No. l£l£>0 



Phase 



Fig. 5 — Digest of Motor-record Information 

This card may be used as manufacturer's mill, department, horsepower 
or speed classification to locate any motor if any of its characteristics 
are given, and it also enables total connected load records to be kept for 
any desired portion of plant. 



side to show any changes in its location. The repair card con- 
tains sufficient information to identify properly the repair part 
in question, permits prompt ordering of replacements, saving 
laborious investigation, and the stock code number allows the 
stock clerk to pick out immediately from his bins a given bush- 
ing or coil, provided that he knows the motor it is to be 
applied on. 

Each one of the cards mentioned is filed in its order, and in- 
formation thereon is kept up to date by the proper cooperation 
of the records department, the testing department and the oper- 
ating or maintenance department. The arguments in favor of a 
system similar to this are many, and even in a smaller plant the 
time saved and the valuable information accumulated by the 



24 ELECTRICAL AIDS TO GREATER PRODUCTION 

tabluation of this data are surprising to one not accustomed to 
the system. 

Conclusion. The preceding discussion is the result of inves- 
tigations and studies in a plant using several thousand motors 
and covers many years' experience with troubles incidental to 
their operation. The repair record is merely typical, to illus- 
trate the point of the discussion. The motor record is substan- 
tially one which is in very satisfactory use to-day. 

PREVENTING INTERRUPTION OF PRODUCTION 

The importance of an adequate uninterrupted supply of mo- 
tive power is appreciated by all production engineers. In many 
cases, however, it is given comparatively little consideration in 
the press of routing, machine layout and other problems, because 
the latter are of relatively greater importance to the production 
engineer. The inevitable result is motor breakdown and conse- 
quent interrupted production when production problems are 
supposed to have been solved and the plant should be taking its 
full load. Many engineers play very safe and install more than 
enough motor-power equipment. This is particularly true in 
the case of munition plants where the supply of money is plen- 
tiful. 

There are two objections to this over cautiousness, however, 
says Sydney Fisher, process engineer, Bridgeport Brass Com- 
pany. One is the fact that the available supply of motors is 
relatively low; hence the rating should approximate closely the 
actual requirements, as otherwise labor and equipment many 
have to wait for power. The other objection involves the oper- 
ating difficulties that inevitably result from over-motoring, par- 
ticularly where the equipment is of the alternating-current type 
and the reactive power is an important consideration. The 
writer has been called in on two cases where the reactive power 
demand has greatly exceeded the average power demand, hence 
causing a breakdown of transforming transmission equipment. 
The design of the motive-power equipment of the plant should 
be placed in the hands of a competent electrical engineer to 
whom all layouts of machinery requiring power should be sub- 
mitted for the selection and location of the motor or motors and 
for any recommendations he may see fit to make. 



S§1 



o 

CO 
<3 



O 



i 



M 

o 

- 

o 



s 

ft 

O 



- 

£ 00 

l-H 

es c3 



O co 
CO > 

H 

Q 












I "* 
• id 

ft 

CM 

-1-3 

esS 



26 ELECTRICAL AIDS TO GREATER PRODUCTION 

The following suggestions on the selection, installation, opera- 
tion and maintenance of motor equipment are based on experi- 
ence at three munition plants. For group drive and individual 
drives requiring constant speed the three-phase, 60-cycle squir- 
rel-cage induction motor is without question the most desirable 
type of motor for industrial work. It is of very simple design 
and very rugged, two factors which make for ease of construc- 
tion, without resulting low cost and large supply and low main- 
tenance respectively. This motor will take sudden load varia- 
tions up to 200 per cent of its rated full-load torque with a com- 
paratively small variation in speed and with small temperature 
rise. This type of motor is very satisfactory for drop-hammer, 
punch-press and upsetting-machine drives, the load on which is 
very variable. 

Fig. 6 gives the load variation on a 25-hp., three-phase. 60- 
cycle squirrel-cage motor driving barrel-rolling equipment con- 
sisting of a hot roll, an 800-lb. (362.9-kg.) drop hammer and 
double hot saw 36 in. (91.4 cm.) in diameter. This motor has 
operated for more than a year during three eight-hour shifts 
per day without breakdown. 

Four hundred and forty volt motors are very satisfactory, the 
cost of wiring to serve them being much lower than that for 
220-volt motors. As to speed, the 1200-r.p.m. motors are 
cheaper, but they give considerable bearing trouble, particularly 
with belt drive. Therefore 900-r.p.m. motors are more satisfac- 
tory. 

The question of group versus individual drive is a very im- 
portant one. Production engineers who have had the bitter 
experience of trying to get maximum production with a poorly 
designed, badly maintained motor equipment are apt to decide 
in favor of the individual drive. Instead of judging any type 
of drive hastily, however, it would be better to consider the rela- 
tive merits of a well-designed group drive and an individual 
motor drive for the same group of machines. To illustrate how 
this can be done consider Fig. 8. The load curve shown is that 
of a drive which has operated without breakdown for eighteen 
months prior to this writing and may be considered a good design. 
An individual motor drive for the same group of machines might 
be determined from the data given on the curve as follows : 

The peak-load 26.1 brake-hp. labeled "Work arrives, machines 



GENERAL POWER PROBLEMS 



27 



take load," is doubtless due to all twenty machines taking their 
maximum load simultaneously, hence the combined friction and 
cutting load per machine would be (26.1 — 5)^- 20 = 21.1/20 = 
1.05 brake-hp., 5 hp. being the line and countershaft friction 
load. To make the equipment flexible enough to cover possible 
changes of spindle speed, rate of feed and depth of cut, it would 
be advisable to provide 25 per cent reserve capacity, hence 
twenty 1.25-hp. motors would be the equivalent of the group 
drive. It should be noted here that the diversity factor which 



LARGE CURRENTS DURING 
, HALF HOUR OPERATION 
1-200- AlfR\ 
I -170 -160 
4 - 160 -170 
2-150-160 
9 - 140 -150 
II - 130 -140 
6 - 120 -130 
13 - HO -120 



OPERATION OF ONE 

IOOOLB.DROP 
75 AMP 20. 7 HP. 



242 V. 



112 
112 
100 
100 
90 
90 



LC 



LC+M 



CONNECTED LOAD 

4 -1000 lb. Drops 
4- 600 lb. » 
4- 600 lb. Operating 
3 -WOO lb. • 



TOTAL AREA 675 
Area occupied ■> 
by Drops In \590 

Operation \ ) 
AMP/ o '«0J60 
HP/b> = 0.007 
xHP/iq$-0.9I 



43.0 
43.0 
36 5 
36.5 
30.5 
30.5 



LOAD TEST NO. I 

7$#P. MOTOR NOl2 
LOCATION 
NO. 27 I FORGE 




L02 103 

Time in Minutes 

Fig. 7 — Load Fluctuations on a Motor Driving a Group of Drop 

Hammers 



exists with the group drive, but is absent in the individual drive, 
would cover small changes of spindle speed, rate of feed and 
depth of cut on about half the machines in the group. 

Comparing the cost of the motor equipment in both cases, 
exclusive of cost of wiring, which would be considerably greater 
for the individual drive and take a greater length of time to 
install, one 20-hp. motor with compensator would cost $460, 
whereas twenty 1.25-hp. motors with starting switches at $102 
would cost approximately $2,040. A small factory having forty 
such groups would require approximately forty 20-hp. motors 
for group drive and 800 1.25-hp. motors for individual drive. 
With the large order balances now carried by the large electrical 



28 ELECTRICAL AIDS TO GREATER PRODUCTION 

companies, it is probable that a better delivery would be obtained 
on forty 20-hp. motors than on 800 1.25-hp. motors. 

Regarding the relative cost and time of delivery of shafting, 
hangers, pulleys, belting and counter-shafting required for the 
group drives and the change gears required for the individual 
drives, both involve steel and labor, two items which are at a 
premium at the present time. 

Power Factor with Group and Individual Drive. The aver- 
age power demand of the group drive is greater than that of the 
individual drive, owing to a continuous friction load required by 
shafting, belting, etc. The friction load varies from 25 to 35 
per cent. On well-designed drives, however, the power factor is 
relatively high and the reactive power demand correspondingly 
low. For the individual drive the average load per motor is 
lower, there being no shafting, belting, counter-shafting, etc., 
and no diversity factor. This low average load coupled with the 
inherently low power factor for small motors results in a low 
total power factor. 

In the case of large plants with a central power station where 
process steam and steam for heating are in great demand the 
additional power demand for friction is very desirable, while 
the high power factor makes for high turbine efficiency. Where 
an outside power supply is depended upon, the expense of power 
for friction is of course undesirable ; on the other hand, addi- 
tional expense is usually incurred by a low-power-factor load. 

The relative ratings of transformers, cables and generators re- 
quired for each type of drive might be compared as follows: 

Kw.g — Group kw. (approximately 80 per cent power factor). 

Kva., = kw.g ~- 0.80 = group kva. 

Kw.i =0.75 kw., (assuming 25 per cent friction load) 

= kw. for individual drive (approximately 60 per cent 

power factor). 

Kva.i = kw.i ^-0.60 = 0.75 kw., -=- 0.60 = 1.25 kw., 

Kva.o 

.. i = 1.25 -f- 1.25 = 1. 

Kva.i 

Inasmuch as the required capacity of generators, cables and 
transformers determined by the kva. load is practically the same 
in both cases the initial investment of this equipment and time 



GENERAL POWER PROBLEMS 



29 



of delivery do not differ. The maintenance of motor equip- 
ment is unquestionably higher with individual drives. This, of 
course, is inevitable with such a large number of units each 
operated by an employee whose chief consideration so far as 
the motor is concerned is to close and open the switch as re- 
quired. Of course, breakdown of the motor involves only the 
shutdown of the machine which it drives, whereas shutdown of 
a group motor entails the shutdown of every machine in the 
group. Serious shutdown of a group motor should be a rare 
occurrence, however, if (1) the drive is carefully designed, if 
(2) adequate inspection of motor equipment is maintained, and 
if (3) an efficient maintenance force is available. 




Fig. 8 — Load Fluctuations in Receiving Mill 

The motor is rated at 20 hp., 238 volts; the length of the line shaft is 
126 ft. Twenty-two belts are used, 50 per cent of which are crossed and 
100 per cent are double. L.C. and M. per sq.ft. = 0.0102; L.C.M. and M. 
per sq.ft. = 0.0173; L. and C. per ft. of line = 0.04; L. and C./L.C. and M. 
=3 0.43; L. and C./M. = 0.75; power machining -f- power L.C. and M. = 
0.70; maximum demand -=- average demand = 1.22. L.C. is line and coun- 
tershaft friction load, M. being machine friction. 



The common method of ascertaining the size of motor required 
is to add the power requirements of the machines driven, as 
given in the manufacturer's catalog, and apply what is com- 
monly called a load factor. This more or less hit-and-miss 
method usually results in the selection of motors either too large 
or too small. A glance at the load curve in Fig. 8 will suffice 
to show that the power required to overcome machine friction 
is only about 25 per cent of the total power demands, the greater 
portion of the power being required for machining. In other 
words, power demand is determined by the class of work done 
on the machine. It is a function of (1) the spindle speed and 
rate of feed, (2) the depth and width of cut, and (3) the di- 



30 ELECTRICAL AIDS TO GREATER PRODUCTION 

versity factor, which depends on the length of cut and the num- 
ber of machines per operator. 

Careful consideration of item 3 is of the utmost importance. 
For instance, even with the same conditions of operation as re- 
gards spindle speed, rate of feed and depth of cut, a larger 
motor is required for a cut 12 in. (30.5 cm.) long in the direction 
of feed than would be required for a cut 2 in. (5.1 cm.) long, 
because a larger number of machines would require power si- 
multaneously. Similarly a one-machine-per-operator condition 
would require more power than a two-machine-per-operator con- 
dition, since the number of machines cutting at the same time 
would be greater. The effect of the diversity factor is illus- 
trated in the curve shown in Fig. 8. The peak load occurred 
immediately after the arrival of the work and was evidently the 
result of all machines operating simultaneously, being consider- 
ably higher than the peaks during normal operation. 

Two ammeters (0-50 and 0-150), the characteristic curves of 
stock sizes of motors (10, 15, 20 hp., etc.) and a few typical 
machine groups to experiment on should provide sufficient data 
for the motor layout design of most of the common machine-tool 
groups. A synopsis of the data needed and of the method of 
calculating the motor-characteristic curves is given below: 

1. Efficiency and power factor at half, three-quarters, full and 

one and a quarter times full-load output for standard sizes of 
220-volt, three-phase, 60-C3 7 ele, 900-r.p.m., constant-speed in- 
duction motors. These data were obtained from the motor- 
manufacturing company's price book. 

2. No-load input and no-load current values, obtained by test on 

standard motors. 

Method of Procedure : 

1. Input-output curves were plotted from above data, 1 and 2. 

Input = output -=- efficiency. 

2. Efficiency curves were plotted from input-output curve, which 

supplied values of efficiency below half full load. 

3. Load-current curves were obtained by substitution in following 

relation : 

P = (1.732IE cos# E) -^- 746. 

1= (746 X P) H- (1.732E cos0 E) = [746 -f- (1.732 X 
240)] X [P-Mcos0X*O] 
= 1.795 X (P -t- cos# X E) • 



GENERAL POWER PROBLEMS 31 

I = load current. 
E = ]ine volts (240 volts). 
Cos0 = power factor given by manufacturer. 
E = efficiency given by manufacturer. 
P = power output (hp.). 

Four points were obtained by calculation, using data No. 1 
and a fifth point from data No. 2. 
4. Power factor curves were plotted using four points from data 
No. 1. An additional point was obtained by substituting no- 
load current and no-load power input in cos# = watt input -f- 

The use of the ammeters and the characteristic curves are 
demonstrated by the data given on Fig. 7. These data were 
obtained from a test on a 75-hp. motor driving a group of drop 
hammers and were subsequently used to design six similar 
drives. 

Good judgment is a very valuable factor, of course. Accu- 
rate data obtained from a few careful experiments and applied 
with good judgment will result in economy of time and capital 
and will assure continuous and satisfactory operation. It is 
desirable from an economic and operating standpoint to design 
for an average load which is not less than 90 per cent of the 
rated load of the motor. Advantage should be taken of the over- 
load capacity of the motor in every case. In this connection a 
chain drive should be used for the main drive, since the pulleys 
supplied by motor manufacturers apparently (from the experi- 
ence of the writer) are not designed to transmit the overload 
which the motor is capable of carrying without slip. 

Inspection and Maintenance Service. Assuming that the 
motors have been carefully laid out, they should run without 
shutdown if given a reasonable amount of care. By care is 
meant adequate inspection to locate the cause of trouble before 
it reaches the danger point and immediate attention by an effi- 
cient maintenance force to correct the cause. It is the policy of 
many plants to expect machine operators and floor foremen to 
report the cause of breakdowns, but such practice does not bring 
satisfactory results since machine operators and foremen are 
responsible for production and that is the chief subject in which 
they are interested. They have neither the inclination nor the 



32 ELECTRICAL AIDS TO GREATER PRODUCTION 

time, if they are attending to their work properly, to keep track 
of service equipment. It is eminently the function of the serv- 
ice department to see that its equipment is kept in proper 
shape to insure continuity of service, and this can only be done 
by an adequate inspection force. This does not necessarily mean 
an increase in the service force, as the work of an efficient in- 
spection force will result in an elimination of trouble to such an 
extent that the maintenance force will have ample time for in- 
spection work and may, therefore, ultimately replace the original 
inspection force. 

Adequate inspection is maintained in one of the biggest muni- 
tion plants in this country, and breakdowns, particularly of 
motor equipment, are very rare. This inspection work is car- 
ried on almost exclusively by maintenance men ; hence, compara- 
tively speaking, the cost of inspection in this case is almost negli- 
gible. 

The inspection of motor equipment should include the obser- 
vation of the following items : 

Motor. 

1. Oil supply. 

2. Freedom of oil rings. 

3. Application of gap gage to air gap. 

4. Main-drive belt tension. 

5. Slip-ring surface. 

6. Speed test. 

7. Motor temperature. 

8. Observation of conditions in shop which would affect the opera- 

tion of motor. 

Control Apparatus. 

1. Condition of make-and-break switches. 

2. Condition of overload release on compensator. 

3. Examination of compensator contacts, particularly on the run- 

ning side. 

4. Inspection of overload relays (timing, damping, etc.). 

5. Oil supply in compensator. 

6. Temperature of compensator — no-voltage-release coil. 

A frequent cause of motor shutdown is defective starting and 
control apparatus. This is largely due to careless manipulation 
of the former and improper adjustment of the latter. It is 
essential, therefore, to provide comprehensive instructions cov- 



GENERAL POWER PROBLEMS 33 

ering the starting and stopping of motors, and to train one of 
the machine operators on each floor for this work. Most of the 
trouble is caused during noon hour when motors are "hobbed" 
in order to place the belts. "Hobbing" is prolific of more 
breakdowns than any other cause with the possible exception of 
seized bearings resulting from excessive belt tension or lack of 
oil. If a motor accelerates too rapidly to permit placing a belt 
safely, the compensator taps should be adjusted to cause a lower 
acceleration. 

An efficient, enthusiastic maintenance force is one of the big- 
gest assets that an industrial plant can have. The word enthu- 
siastic is by no means misapplied as the conditions under which 
these men have to work and the rapidity with which they have 
to work are very trying. Properly directed, an enthusiastic 
force will correct a shutdown in jig time. 

The training of an efficient maintenance force is largely a 
matter of personal contact of the chief electrician or electrical 
engineer with his men. An hour or two per week given to in- 
struction of the men in the fundamental principles of electrical 
engineering and their practical application will accomplish won- 
derful results. 

The electrical engineer should draw up a logical method of 
procedure to determine the cause of motor breakdown. This has 
been found to be a great time saver as compared with the usual 
hit-and-miss methods employed by the average electrician. Such 
a method of procedure might be framed as follows : 

Test temperature of motor by hand. 

1. If temperature of frame, including bearing, is uniform, examine 

fuses or relays ; replace blown fuses and examine relay timing 
adjustment and damping device. 

Start motor and stand by. 

2. If temperature of bearing is abnormal, look in oil chamber. If 

full of oil, examine oil ring to see if it revolves freely. Re- 
set relays or replace blown fuses. Jerk starting lever and ob- 
serve motor shaft and chain or belt. If there is no motion, 
there is a seized motor bearing. Call for emergency motor. 

3. If temperature of frame is uniform but abnormal, replace blown 

fuses or reset relays and start motor. Take speed of motor. 
If speed of motor is less than full-load speed, motor is over- 
loaded. Inquire of floor foreman about changes in operation 



34 ELECTRICAL AIDS TO GREATER PRODUCTION 

and look for seized shaft bearing. If either is the cause, 
notify chief electrician immediately. 

Suggested Procedure in Case of Breakdown. In case of 
motor shutdown the following method of procedure is to be fol- 
lowed unless the cause of shutdown is immediately apparent. 

Overheating of a three-phase motor is frequently caused by 
running single-phase, one phase being broken by a bad compen- 
sator contact on the running side ; therefore examine compen- 
sator contacts on the running side and rectify if necessary. 

The reason for the various steps should be carefully explained 
and every effort made to get the men to memorize the instruc- 
tions. 

The cost of delay in the event of breakdown can be substan- 
tially reduced by installing two motors per section and provid- 
ing an auxiliary jack belt so that either section can be driven 
from the adjoining section. By doing this and providing extra 
cooling for the motor operated the writer has managed to keep 
a large portion of the machinery in similarly divided sections 
running until a new motor could be installed. A 20-hp. motor 
in one case carried 32 hp. for four hours, suitable additional 
ventilation having been provided as mentioned above. 

In conclusion, decide on the best make of motor and install 
it throughout. This will substantially reduce the number of 
spares and spare parts to be kept on hand. As a result the invest- 
ment in stock parts will be minimized, repairs can be made easily 
and less delay will be caused when there is a breakdown. 

POWER FACTOR CORRECTION— AN URGENT 

NECESSITY 

Most of the larger electric systems are already overloaded, and 
something has to be done immediately if further demands for 
power are to be fulfilled. This was particularly true late in 
1918, Will Brown of the Electric Machinery Company, says be- 
cause it was difficult, if not almost impossible, to obtain new gen- 
erating apparatus and distributing equipment, and also because 
the fall lighting load was beginning to overlap the power load, 
leaving no margin of capacity for growth of load. Further- 
more, every one had been warned that fuel would be scarce that 
winter, so power production was further limited. That there 



GENERAL POWER PROBLEMS 35 

had been a shortage of electric power for some time is a fact well 
known to the industry. The two-hundred-million-dollar emer- 
gency power bill was a belated effort by Congress to remedy the 
situation. 

Since power is the basic necessity of all war industries, it 
behooves every one interested in its production and use to con- 
sider how it is going to be secured in quantities which are de- 
sired. Of course, the usual methods of economizing here and 
curtailing unnecessary waste there can still be followed; but 
something more must be done, and that is to consider how poor 
power factor is limiting power and how it can be improved. 
The reduction of power factor has become particularly serious 
since the war, probably because of the fact that much alternat- 
ing-current equipment has been installed and not operated at 
the best loads. 

How a Whole Community May Be Affected. As an example 
of how a community and its power company has been affected 
by low power factor, the general power representative of one 
large central generating station in the East, writes as follows 
under date of August 30, 1918: "We now have a shortage 
of capacity both in generation and transmission, and in order 
to meet the demands of war industries, we are asking our cus- 
tomers to comply with our contract requirements of 80 per cent 
power factor. We have been making tests of our larger cus- 
tomers' operating conditions with an improvement in power 
factor in mind." 

What is true of this company, which serves New Jersey's 
enormous war industries, is true of companies throughout Penn- 
sylvania, Ohio, New York, Illinois, Indiana and other manu- 
facturing states. 

Power factor is a subject confronting not only the power pro- 
ducers but also the users, first, because if the user doesn't help 
to improve power factor he cannot get the power, and, second, 
because improving power factor is going to make it possible 
for him to get more work out of the equipment he has already 
installed. This is something that many industrial plant engi- 
neers have not stopped to consider, and still it is vital to max- 
imum production. The details of the benefits to the producer 
and user will be discussed later, but what has been said should 
be sufficient to point out that cooperation between industrial 



36 ELECTRICAL AIDS TO GREATER PRODUCTION 

plants and power producers is vitally essential now before any 
more time passes. 

Plans cannot be definitely outlined for such cooperation since 
the conditions differ so in different localities, but it might be 
suggested that representatives of central-station companies and 
the industries they serve might find it mutually beneficial to 
discuss plans of power-factor improvement. Having more engi- 
neering information back of them, the central-station engineers 
might point out to the industrial-plant engineers how power 
factor is going to benefit the user and how they go to work to 
locate the causes of poor power factor and improve it. Con- 
sulting engineers might be invited into such conferences and left 
to give the advice necessary to correct conditions where the in- 
dustrial plant is not well equipped with electrical engineering 
talent. At any rate, there is an opportunity for cooperation, 
and not much time or money will have to be expended in getting 
results, as the remedy can be applied at once. 

It is a curious fact that many men view low power factor as 
an abstract evil that is causing the "other fellow" lots of 
trouble. They readily admit the importance of high power 
factor, but cannot seem to realize that they themselves are help- 
ing to make matters worse — that right in their own plant 
power is being wasted and money is being lost. Hundreds of 
central-station officials write that the greatest obstacle to power- 
factor improvement is indifference. At Niagara Falls indiffer- 
ence on the part of a large user was responsible for a large law- 
suit, involving more than a hundred thousand dollars — all for 
wattless current. Indifference is keeping many induction mo- 
tors runnings at poor power factor when it would be just as 
easy to run them at good power factor. 

In the past large central stations which had excess power to 
sell were not over-particular about anything but load factor. 
The times are different" now. Electric power is going to be sold 
and used under restrictions as to power factor. Central stations 
are by no means anxious to impose penalties, but they may be 
forced to do so if those who cause poor power factor do not 
correct conditions. This does not mean that the average cost of 
power is going to be increased ; on the contrary, it is very likely 
that this will tend to decrease certain power rates. The power 
user who operates his plant so that his power factor is kept rela- 



GENERAL POWER PROBLEMS 37 

tively high will actually be receiving a bonus in the way of 
reduced rates. 

However, rates based on power factor are only a means to an 
end, and if the customers once realize how big an economy they 
can secure by a little attention to motor operation they will 
never again turn to old haphazard methods, and when added to 
this is the very present possibility that power in some cases can- 
not be secured at all unless power factor is improved, surely the 
power customers will get busy and improve their loads. 

There is one thing encouraging about the situation ; nine tinies 
out of ten when the discovery is made of what is really causing 
poor power factor it is possible to make considerable improve- 
ments without any additional apparatus. There is always a bet- 
ter way of using equipment now installed, and the advantage 
is that the remedy can be applied at once. 

Picture of Waste from Low Power Factor. To visualize the 
losses brought about by low power factor, imagine a great hill 
of junked electrical apparatus — alternators, transformers, oil 
switches, thousands of miles of copper wire, lying tangled all 
over "no man's land." That's about what it means when we 
say in cold engineer's English that low power factor cuts down 
the capacity of generating, transmission and distributing appa- 
ratus. Alongside of this first hill is a second hill, smaller it is 
true, but very formidable. Here are piles of steam engines, gas 
engines, waterwheels and steam turbines that are giving no serv- 
ice at all. This is the condition that exists when we say that 
part of the capacity of prime movers is wasted because of low 
power factor. In addition to this there is another waste that 
cannot be shown as a piled-up hill of wreckage, but it exists 
nevertheless. It is the lowered efficiency at which all prime 
movers are forced to operate when they are working at part 
load. 

Turn now to a water-power plant. Over the giant spillway 
thousands of tons of water is pouring, all wasted because the 
wheels can be operated only at part gate, this in turn being due 
to the reduced rating of the generators caused by poor power 
factor. The water can't be stored, the generators can't carry 
any more current, and so all this water power is going to waste 
just when it is needed most. Every kilowatt of PR loss means 
burning a certain amount of coal. The PR losses at 70 per 



38 ELECTRICAL AIDS TO GREATER PRODUCTION 

cent power factor are more than twice as large as the PR losses 
at unity power factor (same power delivered in both cases). 

Then try to imagine the accidents and shut-downs happening 
every day due to overheating of conductors and consequent 
break-down of insulation. Low power factor is indirectly re- 
sponsible for much of this contributory damage. Overloaded 
apparatus means work for the troubleman. Break-downs are 
more serious to-day than ever, as the time involved in making 




s 5 § 



S o ^ o s> o ^ ^ ^ o s» 

i z R Losses in KW and IR dr.q& in VOLTS — 



Fig. — How Tc^yer Factor Affects I 2 R Loss and Potential Drop in 

Conductors 



repairs is greater because of the shortage of spare parts as well 
as the shortage of men to do repair work. A shutdown due 
to a burn-out to-day is likely to result in considerable loss in 
plant production. 

Every motor on such a system is working under the handicap 
of poor voltage regulation, and sometimes it doesn't work at all. 
Furthermore, poor power factor is usually an indication that 
alternating-current apparatus is working considerably below 
rating. This means that maximum use is not being obtained 
from equipment and is particularly serious because every pro- 
ductive hour counts to-day as never before. Imagine the car- 
loads of material — iron, copper, steel, etc. — and the skilled labor 
as well — which could be released for other work if by some 
magic the power factor of the peak load on all electrical systems 
could be raised to 100 per cent ! 

Evil effects of low, lagging power factor are too well known 
to need much discussion. But it is one thing to understand 
statements in a general sort of a way and quite a different thing 
to be brought rudely up against the facts themselves. 



GENERAL POWER PROBLEMS 39 

Typical Examples of Effects. Here are typical examples 
of things that are now happening : 

Case 1— "We designed a line, 22 miles (35 km.) in length, 22,000 
volts, for a certain kilowatt load, at 80 per cent power factor. After 
the load was connected, including a very large hoist, we found the power 
factor during the hoisting period would drop as low as 50 per cent. 
This doubled the kva. in the line and made regulation so poor that the 
hoist could not be operated. We must practically double our line ca- 
pacity in order to take care of the wattless currents." 

Case 2. — "At a certain power station we had three generators, giving 
service to the town, and one large power customer with a connected load 
of 300 hp. in induction motors. This customer's load factor is 80 per 
cent and the power factor is 60 per cent. At our request customer in- 
stalled a synchronous condenser, receiving 10 per cent discount on his 
net bill. This resulted in raising the power factor to 85 per cent and 
enabled us to carry day load on two units, whereas it was previously 
necessary for us to run all three units to handle this load." 

Case 3. — Hodenpyl, Hardy & Company of New York state that on 
some of their large contracts, particularly in Ohio, they have allowed a 
better rate for energy consumed at specified high power factor. This 
has had the effect of inducing customers to install corrective apparatus, 
and in a number of cases where contracts approximated 10,000 kw. or 
more customers immediately installed synchronous condensers at their 
own expense. 

The isolated plant which generates power for its own use is equally 
interested in providing for high power factor. This should be con- 
sidered when apparatus is installed and also when planning methods of 
operating machines and motors. 

Causes of Poor Power Factor. While certain types of alter- 
nating-current apparatus are undesirable in point of power 
factor, they have not been generally developed commercially or 
if they have they are not used extensively. Therefore the usual 
cause of poor power factor is not so much the result of poor 
design as it is of poorly planned installations. This is evident 
from the fact that most commercially developed induction 
motors produce a power factor as high as 90 at full load and 
never much lower than 65 in the smaller sizes and lower speeds. 
On the other hand, however, if the motors are incorrectly applied 
to the machines (that is, if the average load is much less than 
the rated load of the driving motor), the power factor will be 
considerably lower than it would be if the motor were properly 



40 ELECTRICAL AIDS TO GREATER PRODUCTION 

loaded as shown by the curves in Fig. 10. Thus it may be seen 
that unless careful attention is given to diversity of load 
in grouping machines and to actual power requirements, very 
low power factor may result, especially since it is usually the 
practice to provide a liberal margin of power instead of to 
depend on the overload capacity for carrying peaks. What is 
true of induction motors regarding power factor is also true of 
nearly ail alternating-current apparatus — the farther below 



100 



90 



£0 



70 



&60 

0- 



k 

o 



V4 



Load -- 



4/4 



54 



50 



40 



0- 30 



20 



10 

































( ^C^p: 


FtLU} 








^»S 








S'Vl^B 
WW* 








Y 






A 

f A 


•f 










M 


«fiS 


■S\ 












A 


'/// 


J 


\y 


^ 








/ 




ty 












V 

7 


w* 


f> 










// w 

AX* 


f 
















y 


























n\ l / / 
















/ 
















































WWII f 


























































J 


1 , 













Fig. 10 — Probable Power Fac- 
tor WITH IXDUCTIOX MO- 
TORS 



rated load it is operated the lower the power factor produced. 
Single-phase arc furnaces are also productive of low power 
factor even when working at normal rating. 

Some engineers argue that individual drive is best because 
then motors can be selected for a definite load and can hence be 
operated at the best power factor as well as the best efficiency. 
Others maintain that the advantage which can be taken of diver- 
sity makes group drive preferable because such a large margin 
of rating does not have to be provided for peak loads. Each 



GENERAL POWER PROBLEMS 41 

argument has something in favor of it, but it will usually be 
found that the average load on a well-applied group-drive motor 
is closer to the motor rating than is the case with an individual- 
drive motor, so the resulting power factor must necessarily be 
better for group-drive motors. 

The application has a great deal to do with the results, how- 
ever. Among the principal breeders of power-factor troubles 
are hoist motors, which draw a large current in starting, and 
individual drive motors that require large amounts of power in 
starting and carry flunctuating loads. For instance, witli re- 
ciprocating pumps it is not uncommon for the load to vary 
from zero to full load periodically. Meanwhile almost as much 
current is drawn from the line at part load as at full load. 

In textile mills where many small induction motors are driv- 
ing individual machines there is also apt to be low power factor. 
This typical example comes from an official of the Titusville 
(Pa.) Light & Power Company: 

Several years ago as manager of a central station I made a contract 
with a new silk mill for power at a rather low rate. Instead of group 
drive, which we thought the mill owners would use, they installed some 
350 or 400 ^-kp., three-phase motors, one to each loom. After a loom 
was started it required very little power to keep it in operation, result- 
ing in a 35 per cent power factor and a 35 per cent load factor during 
period of operation, fifty-four hours per week. 

We ran a special circuit from our plant to a substation at this mill, 
which was situated close by, and installed in the substation three 100- 
kva. transformers. When the mill was not in operation and no energy 
was being used, our instruments showed that the silk-mill circuit was 
using in capacity and core losses 25 kva., about 5 kva. of which was 
core loss, the rest being due to the low power factor of the unloaded 
transformers. As there were some motor-driven fire pumps connected, 
it was impossible to cut out the circuit during the time the mill was not 
in operation. 

Since then I have endeavored, wherever it is possible to do so, to 
place large power customers on synchronous converters or synchronous 
motor-generator sets. It is usually possible to do so as most manu- 
facturing plants desire variable-speed motors. 

Low power factor may also be produced by using direct- 
connected induction motors to drive low-speed machines like 
compressors. At Punxsutawney, Pa., for instance, there is a 



42 ELECTRICAL AIDS TO GREATER PRODUCTION 

certain railroad shop where four 100-hp. induction motors were 
driving air compressors. These reduced the power factor at the 
plant to 65 or 70 per cent, causing considerable trouble owing to 
insufficient fuse capacity and excessive overload at the power 
house. These power users have now installed synchronous 
motors which float on the line and correct the power factor. It 
would have been much better from all standpoints if the original 
compressor motors had been of the synchronous type. 

Where direct-current power is required it has often been the 
practice in the past to use direct-current generators driven by 
induction motors. These always give considerable trouble be- 
cause of the reactive (wattless) component they produce. The 
following extract from a report concerning the Jamestown (N. 
Y.) Light & Power Company describes a case in point: 

There was a certain large power consumer who had ordered a 200-hp. 
induction motor-generator set. We immediately showed him that he 
could improve his power factor by installing a synchronous motor-gen- 
erator set. He changed his order and took a synchronous motor of a 
larger capacity, which gave a surplus beyond the actual power required 
and gave a lot of condenser capacity for power-factor correction. We 
gave him a better rate for this, which made him see that he could af- 
ford to pay the additional cost of the motor. He is glad that he made 
the change. 

How Lagging Power Factor Works in a Circle. Lightly 
loaded transformers introduce considerable reactance in a cir- 
cuit. Here we can see the effects of lagging power factor work- 
ing in a circle. When power factor is low, excessive current 
must be carried and this necessitates larger transformers. These 
transformers in turn, when lightly loaded at off-peak times, tend 
still further to lower the power factor on that feeder circuit. 
Many of these oversized transformers scattered over a system 
have considerable to do with lowering the over-all power factor. 

Regarding this cause of low power factor, the Penn Central 
Light & Power Company states : 

We have had several cases of trouble with power transformers caused 
by low power factor, the transformers being overloaded in kva. while 
the actual output in kw. was far below the transformer rating. We 
have also experienced some trouble with overloaded lines due to highly 
inductive loads. 



GENERAL POWER PROBLEMS 43 

While poor power factor is usually a result of negligence in 
planning the installation, it was caused during the war to a great 
extent by the inability to secure the right size of motor for an 
installation. Since the principal problem before manufacturing 
plants was to produce quickly, they installed larger motors 
than necessary where it was difficult to secure the right size, 
being willing to invest more money and forego the better effi- 
ciency and power factor of the correct motor for the more expe- 
dient method. 

In other cases poor power factor has resulted because of 
change of load due to change in use of machines. This has no 
doubt contributed considerably to the poor power factor now 
obtained, since many plants changed their business entirely to 
engage in war service, utilizing their old equipment, but for 
entirely different duties. 

Even those which have not changed their ordinary business 
may handle such totally different products one month from what 
they do another that the average loads on the motors, and conse- 
quently the power factors, will be considerably altered. The 
improper use of starting and speed-control devices may also 
cause poor power factor. 

What to Do When Poor Power Factor Is Evident. When 
it becomes evident that there is a condition of bad power factor 
something should be done to discover the real sources of trouble. 
To locate the individual causes will take time but will not involve 
the use of many or expensive instruments. This last task is 
really up to the industrial plants, although they might be in- 
structed how to conduct tests by the local central station if they 
are not well enough equipped with electrical engineering help to 
undertake them alone. 

Plants which have separate feeders to each motor with am- 
meters, voltmeters and wattmeters, etc., permanently installed 
on each circuit can determine the power factors of their motors 
so readily that these will be passed over. Many plants, however, 
have feeders running to different distributing panels and have 
no instruments on each individual motor. In such cases port- 
able test sets can be quickly rigged up at small expense and 
arrangements made so they may be connected in circuit without 
interrupting service. This detail can be left to each individual's 



44 ELECTRICAL AIDS TO GREATER PRODUCTION 

ingenuity, although one or two methods which might be used 
will be mentioned. 

For example, arrangements can be made for connecting test 
sets to the jaws and hinges of the motor's main switch, and 
then when everything is in readiness for making the tests the 
main switch can be opened and readings taken. Instead of 
clamping the testing cables to the switch jaws, they might be 
attached to the end contacts of blown fuses inserted in the reg- 
ular fuse clips. Of course, in such cases fuses rated to protect 
the motor should be included in the test circuit, and in any case 
the instruments must be of such size that they will not be in- 
jured. 

Since load surveys should be made periodically, it would be 
advisable to arrange the main switches for ready connection of 
the testing equipment. For the same reason the testing equip- 
ment should be assembled permanently in portable form. As 
power factor is so closely associated with the load factor of 
motors, it will usually be satisfactory to test only for load to 
see if it is near the rating of the motor, unless there is some 
question as to whether the motor is the proper type to use. To 
obtain records which will be suitable as a basis for making 
changes, graphic charts should be taken, and preferably over a 
period which will include all ordinary fluctuations. 

Such records will not only indicate which motors are respon- 
sible for the poor power factors but will also give a basis for 
replanning the motor drives. Although at first it may be neces- 
sary to select the size of motor on the basis of the power re- 
quirements as given by the machine manufacturer, it would be 
advisable finally to determine the nature and magnitude of the 
load by careful tests and then readjust the motor drives to agree 
therewith. 

The power factor of other apparatus than motors can be deter- 
mined in a similar manner. 

How to Correct Power Factor. If the poor power factor 
seems to be due to some inherent characteristic of the apparatus 
operated, about the only remedy is to have the manufacturer 
adjust it or else provide some corrective apparatus such as syn- 
chronous motors, synchronous condensers or static condensers. 
AYhen time is limited these remedies are particularly effective, 
as they may be applied without interrupting service, In view 



GENERAL POWER PROBLEMS 45 

of the fact that synchronous motors can now be used for various 
applications x as well as power- factor corrective purposes, it is 
well to bear them in mind when making new installations and 
decide whether they should not be installed in the first place. 
Since most cases of poor power factor are due to poorly planned 
induction-motor drives, the remedy is to make use of load rec- 
ords in reapplying them. From such records it can be deter- 
mined whether individual or group drive is best and which ma- 
chines should be grouped together. The selection of group or 
individual drive and the grouping of machines depends on so 
many factors that they will not be discussed here, but the reader 
is referred to other articles which have appeared in different 
issues of the Electrical World. In this connection the writer 
(Will Brown) emphasizes, however, that care should be exercised 
in selecting the type of motor to use and then so to apply the 
motors that they will operate as near rating all the time as pos- 
sible. Sometimes substituting a smaller motor for a large one 
and equipping it with a flywheel to help carry the peak loads 
will improve power factor. 

Individual motor drive can often be carried too far. There 
are times when improvement can be brought about by combining 
a number of machines to be driven from the same line shaft. In 
some cases a synchronous motor of liberal capacity, either belted 
or directly coupled, could be installed to drive the line shaft. 
This would serve the double purpose of providing ample power 
to carry \he load over all peaks and providing additional con- 
denser capacity at periods of light load for supplying magnetiz- 
ing kva. to the rest of the system. Whatever slight losses or 
inconvenience might be caused by the belts and shafting would 
be more than offset by the decreased PR losses throughout the 
plant. The result would be better voltage regulation and pos- 
sibly a better rate for maintaining higher power factor. 

It is interesting to note that numerous plants have been saved 
from power-factor troubles by the use of synchronous motor- 
generator sets. Many central-station companies have induced 
customers to install synchronous motors of sufficient kva. rating 
to maintain at all times a power factor of 90 per cent leading 
(or lagging) while driving the direct-current generators. 

i For applications to which synchronous motors are suited see section on 
Motors and Control. 



46 ELECTRICAL AIDS TO GREATER PRODUCTION 

How to Encourage Power-Factor Improvement. Decreased 
efficiency itself is not always a sufficient spur to make the plant 
owner look for a remedy. The possibility of not getting any 
power at all unless correction is made may wake up some indif- 
ferent power users. On the basis that poor power factor is 
usually caused by underloaded motors another inducement can 
be advanced — that improving power factor will release equip- 
ment to take on new loads caused by growth in business. Pos- 
sibly a penalty for low power factor is needed to make some 
factories act. Plant owners would discover that they could put 
in smaller motors and move the old motors up to larger loads, 
and thus really save money on original motor costs. They would 
also obtain a better rate for good power factor. The power- 
factor penalty clause would not remain as a fixed charge against 
factory production, but would bring about increased savings 
both to the power customer and to the central station supplying 
the power. 






CHAPTER II 

DISTRIBUTION, TRANSFORMATION, 
SWITCHING, AND PROTECTION 

EFFECTIVE DISTRIBUTION OF FACTORY POWER 

Notwithstanding the efforts made to direct careful attention 
to the problem of motor application in factory work, there is 
every likelihood that distribution circuits for supplying the 
motor and lighting equipment in many factories will not receive 
the necessary consideration unless special thought is given to 
them by the management. It is reasonable to expect that in a 
new plant the distribution circuits will usually be planned with 
due care to meet the initial needs. The typical factory, how- 
ever, and more particularly the machine shop, requires continual 
rearrangement of machinery, and the tendency of the electrical 
department, in meeting calls for hurried changes in positions of 
motors, is to utilize as far as possible the existing wires in the 
various sections of the plant. One natural result is confusion 
in the circuits, with unbalanced load conditions, excessive power 
losses and an undue voltage drop in the overloaded circuits and 
accompanying reduction in production of the machine tools or 
other machinery supplied. 

Sometimes, there is a tendency to forget that the electric cir- 
cuit is the vital connecting link between generating machinery 
and motors or lamps. It thus takes the place of line shafting 
and belting with their high mechanical losses, and introduces 
more effective means for power supply and at the same time 
makes longer extensions possible than could be realized with the 
older mechanical methods of distribution. 

Their very flexibility is one reason why circuits are overlooked 
so easily and are allowed to become inferior to the well-balanced 
status which may have existed when the plant was constructed. 
One large manufacturing establishment is known which has re- 
duced circuits to diagrams or "wiring maps" which form part 

47 



48 ELECTRICAL AIDS TO GREATER PRODUCTION 

of the records of the electrical division. Every effort is made to 
keep them up to date and promote their regular use in wiring 
work. 

The value of suitable standardization for the factory distribu- 
tion system should not be overlooked, since the addition of equip- 
ment must be governed, in part at least, by the adaptability of 
apparatus on the market to the classes of circuits available in 
the plant. A leading consideration in the lighting equipment, 
although it may be relatively unimportant in the motor problem, 
is that of maintaining rigid separation of power and lighting 
circuits so that the latter may be protected against voltage vari- 
ations probable as a result of changing load conditions imposed 
on the motors. 

When advocates of scientific management look upon a IV2 P er 
cent improvement in production efficiency as sufficient to war- 
rant extended efforts to better the manufacturing methods, any 
part of an electrical system like the supply circuits demands 
sufficient attention to insure the maintenance of highly effective 
operating conditions. 

TRANSFORMER INSPECTION AN ECONOMIC MEASURE 

Thorough inspection of all distribution transformers returned 
from circuits should be made before they are again issued for 
service, first to lessen the chance of failure after replacement on 
the lines, and second to minimize the labor required in making 
the installation. Chances of failure are decreased if trans- 
formers are issued thoroughly clean and dry and with leads and 
bushings intact. Moreover, it is evident that minor repairs 
and adjustments can be made better and cheaper in the shop 
than on the job. 

Bushings Need Close Attention. Bushings should always be 
carefully examined, as they are a frequent cause of failure. A 
break is not always evident from a casual examination, and each 
bushing should be shaken to disclose any looseness. A broken 
or loose bushing, especially a primary bushing, should always 
be repaired before the transformer is again utilized, since it is 
almost certain to break down in wet weather and may, under 
certain conditions, cause a burn-out of the transformer windings. 
As most bushings are broken in handling transformers after 






DISTRIBUTION, TRANSFORMATION, SWITCHING 49 

shipping crates have been removed, means should be provided 
for protecting them. Cylindrical types, whether plain or corru- 
gated, usually become coated with dust whenever there is any oil 
leakage, and breakdown often results. 

In renewing bushings in any line of transformers advantage 
should be taken of the most recent designs that may be accom- 
modated in the outlet holes. It is important that bushings which 
are suitable for the service be chosen. Substitutions should not 
be made unless the new type is superior to the old. A full sup- 
ply of spare bushings should be carried in stock so that make- 
shifts will be unnecessary. A blue-print schedule showing the 
catalog numbers of primary and secondary bushings required 
for each tank number should be prepared with the assistance of 
the manufacturers for each line of transformers handled. This 
will be found of service both in expediting purchases and in 
selecting repair parts from store-room stock. 

When installing new bushings a grade of sealing compound 
such as is specially recommended by the manufacturers for this 
purpose should be used. All of the old compound should be re- 
moved before the new bushing is placed. If the bushing is of 
the type set in with babbitt (those inserted from the outside are 
usually set in with babbitt, paper lock washers or some similar 
device), this metal also should be completely removed. In chip- 
ping out old bushings and compound provision must be made for 
catching the scraps to prevent their falling into the coils or 
bottom of the case. Bushings of the curved styles are best made 
up complete with leads before insertion in the transformers. 
The more simple styles, which are easily filled with compound, 
may be filled in place. 

Heating Compound to Right Temperature. Care must be 
taken to heat the compound to the proper temperature before 
pouring; otherwise cracks will result. The entire corner of the 
case in which the bushing is placed should be heated so that the 
compound will not be chilled on striking the metal. To chill the 
compound will often result in a leak between it and the case. 
Much of the oil leakage which occurs around leads and bushings 
is not caused entirely by siphon action along or through the lead, 
but may be due to cracks between the bushing and the sealing 
cement or between the latter and the case. This leakage will not 
occur unless oil is slopped onto the compound, but it is prac- 



50 ELECTRICAL AIDS TO GREATER PRODTTCTIOX 

tieally impossible to avoid this in han dling - a filled transformer. 
To avoid leaks of this character, not only should hot compound 
be used, but the surface of the compound above the bushings 
should always slop e in fa ~ard the center of the case. This can 
be effected by tilting the transformer while the compound is 
being poured as well as while it is hardening. Where the com- 

:■:: :'. azhrr z'z.r ir—rii: _?.- — : :: ;iz ':■= : V Z .. .- - ... -:_t 

also makes it possible to raise the level of the cement above the 
~:z .z z'--. 'zzSzlzzz s: ~~-Zz ~1t " \^L:l ^ ini --..--- i_iv '.- zilrl 
in :i: :ttTl~:: i 

Bushings should be kept clean. It is a good plan to incor- 
porate in all directions covering the installation of transformers 
a note to wipe bushings carefully after the transformer is in 
place. Most of the :il ~hieh. if left isMng. are 

so likely to cause breakdown are accumulated during transpor- 
tation from the store room to the job. If the bushings are 
cleaned after the transformer is hung, this cause of trouble is 
largely avoided. When transformer tanks are being painted 
care must be taken not to get paint on the bushings, as the rough 
paint surface will tend to gather dust. Bushings of the larger 
types should be wrapped with cloth or paper while eases are 
being painted. 

How Trouble with Leads May Be Prevented. Xext to bush- 
ings, leads require most frequent attention. They are often 
broken in handling or are cut short when transformers are re- 
moved. In addition, they deteriorate because of the siphoning 
of oiL Secondary leads of the types of transformers under dis- 
cussion are invariably rubber-covered. Primary leads are 
usually rubber-covered, although some manufacturers have re- 
cently used varnished cambric insulation for voltages of 11 kv. 
and up. Each material has its advantages. Rubber withstands 
weather and moisture well, but it is deteriorated rapidly by oiL 
This weakness is its most serious defect as oil is often siphoned 
over the leads. Tarnished cambric, on the other hand, while 
benefited by oil. does not withstand weather well when protected 
only by a braid covering. It is easily dried out by hot weather 
and is liable to absorb moisture in wet weather. These remarks 
apply, of course, only to the leads outside of the case; those 
inside are alwavs insulated with varnished cambric 



DISTRIBUTION, TRANSFORMATION, SWITCHING 51 

In arranging for shop repairs to transformer leads it is first 
necessary to prepare a schedule of cables to be used in making 
renewals, in order to secure uniformity in purchases and repairs. 
This is preferable to attempting to replace the old lead with one 
precisely similar in size, insulation and stranding to that in- 
stalled at the factory, since in the past manufacturers have dif- 
fered considerably as to these details in transformers having 
identical ratings. To follow these deviations would require an 
unnecessarily elaborate stock of cable. A schedule which has 
proved satisfactory in practice is given on page 55 for 2300-volt 
transformers. The cables selected, especially those used for pri- 
mary leads, have uot been chosen exclusively on a basis of their 
usefulness as transformer leads, but also with a view to their use 
in the wiring of substations and similar work, in order to avoid 
the carrying of overlapping stocks. All cables are specified as 
single-braid, rubber-covered. However, if any are to be used 
extensively in outdoor work, as for instance in wiring between 
cut-outs and transformers, they may be specified as single-braid 
and tape. The rubber insulation is that specified by the Na- 
tional Electric Code. 

The greatest difficulty in installing leads is to prevent the 
siphoning of the oil. If this happens, the oil will rapidly dete- 
riorate the rubber of the leads and in addition will gather dirt on 
leads and bushings and thus increase the danger of breakdown. 
Where the primary terminal blocks are under oil, as is the case 
in most recent types of transformers, solid conductors may be 
inserted between terminal block and bushing to prevent the si- 
phoning which would be caused if stranded leads were used. 
Where stranded conductors are used the splice between the in- 
side portion of the lead (which is insulated with varnished cam- 
bric) and the outside rubber-insulated part, as well as all inter- 
stices between strands for a short distance on each side of the 
splice, should be thoroughly filled with solder. 

The splice in primary leads should be placed so as to be com- 
pletely surrounded by sealing compound, and the short, bare and 
solder-filled portions on each side of the splice should likewise 
be covered. A wrapped splice is generally used. Secondary 
splices and some of the simpler primary splices are placed 
above the compound. The varnished-cambric insulation of 
the secondary should be started above the oil level. After 



52 ELECTRICAL AIDS TO GREATER PRODUCTION 

filling a bushing with compound, tape should be wrapped around 
the outgoing lead at the point where it leaves the bushing to 
prevent the compound from running out before it has set. After 
the cement has hardened this tape should be removed ; otherwise 
all the oil which may leak between lead and compound will 
gather at this point and rapidly eat away the insulation. 

Instructions should be issued to transformers' installers cau- 
tioning them asainst handling transformers bv the leads. Trans- 



" INSULATION 



FILLING 
HOLE - 



WRAPPED AND [I 

5C.SEP£D -.J. •' 



.Fill Interstices between 

Strands with Solder 

to this Point 




—■Stop End with doth 
while filling 

RUBBER INSULATION 



flUKKIMH TEST REPORT *• 1072 
RtADY roRsawa 

(■W in. (Me 1J1- 

TcsW br 



nn. tausowa its won •» 1 072 




Cm\tu 




K. W, Ty»e 


V.fe HT 


VokIT 






r„ r- kmfi 


los4*tiM V«to 


■*■ 


Retard MtfTsM fry 
lepairs mttumitm 


Mrts iKUiW-lteMfta 











■ urriciCMD 



ijn<B..«m. tOHrtSIO »1072 
Trusferaer lift. H* 

(jeaoty K. W 



Figs. 11 axd 12 — Bushing Construction that Pretexts Siphoning; 
Three-part Transformer Test Report 



formers are frequently dragged along the ground or truck bed 
by the leads or are kept from swinging into the pole when being 
raised by lines attached to the leads. This practice results in 
many broken leads and bushings. 

When new leads are installed they should be made long. In 
some types of pole installations one additional foot of primary 
lead will permit direct insertion of the lead into the primary 
cut-out without a splice. 

Some installers make use of the connectors provided on the 
leads by manufacturers, and use care in handling them ; others 



DISTRIBUTION, TRANSFORMATION, SWITCHING 53 

appear to consider them superfluous and often cut them off. In- 
structions should be given to use these whenever present, as they 
are considerable labor savers, especially in the larger sizes, and 
will give no trouble if properly installed. Any connectors 
which are not used should be left taped to one of the leads so 
that they will be available if necessary in some future installa- 
tion. In removing transformers foremen should be cautioned to 
cut the leads between the connectors and the line and not the 
leads between the connectors and the transformers. The con- 
nectors may then be saved in the shop. Many leads are cut so 
short through carelessness that they must be replaced before the 
transformer can be reissued for service. 

Painting of Cases and Care of Oil. Cases should be repainted 
whenever transformers are brought in from the lines, unless they 
have been installed only a short time. Sheet-steel cases espe- 
cially will deteriorate rapidly unless protected by paint and if 
rusted should be given two coats. Before paint is applied it is 
necessary to clean the case thoroughly with distillate and a steel - 
wire brush to remove all dirt and oil. A good quality of turpen- 
tine asphaltum paint will be found serviceable for this work. 
If a system of location numbers is in use, they should be 
restenciled on transformer cases as soon as they are slightly 
obliterated. A white-lead ' and linseed-oil paint should be used 
for this purpose. Stencils 2y 2 in. (6.35 cm.) high may be 
readily deciphered from the ground, still they are small enough 
so that four or five figures may be placed on the smaller-size 
cases. 

If the transformer has been installed for several years, it is 
preferable to draw off the oil for testing and treatment as soon 
as it arrives on the testing platform. On the other hand, if the 
transformer has been on the lines only a short time and the oil 
seems clear and without a burned odor, it need not be removed. 
In the case of the larger sizes of distribution transformers, a 
sample should be drawn from the bottom of the case with a 
"sneak" for a moisture test. All transformer oil should be 
carefully tested, handled and stored in accordance with the rec- 
ommendations 1 of the apparatus committee of the National 
Electric Light Association. Men cannot be cautioned too often 

i Proceedings N. E. L. A., 1917, Technical and Hydroelectric Section, 
page 281, Also available in booklet form. 



54. ELECTRICAL AIDS TO GREATER PRODUCTION 

against handling oil in the open in damp or foggy weather. 
Companies utilizing distribution transformers of two voltages 
will do well to reserve new oil for the higher- voltage equipment 
and use the seeond-hand treated and filtered oil in the lc 
voltage apparatus. 

When possible, transformers should be filled with oil bef 
they leave the store room: this, however, is not always possible. 
If the old oil is not removed when transformers are returned 
from the lines, an inspection should be made to see that the oil 
is up to the proper level. Schedules of transformers showing 
tank symbols and quantity of oil required for each line of tr 
formers in service should be readily available. It should be 
noted that transformers of the same make and type but of dif- 
ferent form may require quite different quantities of oil. 

Cleaning of Transformers and Detection of Flaws. The 
cleaning of the soils ::' transformers removed from the lines re- 
quires careful consideration, especially if they have been in- 
stalled a considerable time and sludge has been precipitated by 
the oil. The elimination of oil deposits from the circulating 
ducts is particularly essential since their effects are cumulative. 
By impeding the oil circulation they cause the transformer to 
overheat with a given load, which in turn increases the sediment. 
An air-transil-oil spray is effective in flushing the ducts. When 
the oil is drained off it will also clear any moisture which may 
be present at the bottom of the case. 

Many transformers cannot be properly cleaned without re- 
moving the coils from the case ; this is especially true where the 
sediment has thickened. Some of the older types of transformers 
which have no oil ducts between coils should always be removed 
and cleaned by scraping, as a thick coating is generally to be 
found on the coils caused by the lack of circulation. Care must 
- osed in scraping I id damaging the insulation. An air- 

distillate spray will be found effective for this kind of cleaning, 
but should not be used unless the transformer is dried out before 
being placed in service. A distillate spray should not be used 
within the fcesl :>m. owing to the fire risk. A cast-iron grating 
with removable containers should be provided on the tr 
former platform for draining coils and cases : otherwise oil will 
be scattered about. By this means considerable oil or distillate 
can be saved, as the oil can be filtered for re-use. 



DISTRIBUTION, TRANSFORMATION, SWITCHING 55 

Cases should be examined for leaks. A crack in a cover may 
permit the entrance of sufficient moisture to cause breakdown. 
Cast-iron cases when cracked may be welded with an oxy-acety- 
lene torch ; sheet-steel cases may be repaired by brazing or weld- 
ing. Drain plugs should also be examined and set in with red 
lead if leaky. Felt strips should be carried in stock so that when 
those in service are lost or worn they may be replaced. It is 
important that these be kept effective. 

Hanger irons and lugs should be examined for cracks and 
flaws. When transformers are returned from the lines it is ad- 
visable to arrange some system by which the hangers are kept 
with them or properly marked so that they cannot be mixed with 
others. 

TABLES I AND II— CABLES TO USE IN RENEWING 2300/460-230-115- 
VOLT TRANSFORMER LEADS 





Peimari 


■ Leads 








Transformer 


Size 


Insulation 


No. 


Class 


Size (Kva.) 


of Lead 


(^ths of In.) Strands 


2,300-volt 


lto5 


12 


8 


7 




7% and 10 


10 


8 . 


7 




15 and 20 


8 


8 


7 




25 and 30 


6 


8 


7 




37 y 2 and 50 


4 


8 


7 




75 


2 


8 


19 




100 


1-0 


8 


19 




Secondary Leads 








Transformer 


Size 


Insulation 


No. 


Class 


Size (Kva.) 


of Lead 


(% 4 tlis of In.) Strands 




1 to 3 


8 


3 


7 


400-230-1 15-volt 


5 


6 


4 


7 




7V 2 and 10 


4 


4 


7 




15 


2 


4 


19 




20 and 25 


1-0 


5 


19 




30 


2-0 


5 


37 




37% and 50 


4-0 


5 


37 




75 


400,000 cm. 


6 


37 




100 


500,000 cm. 


6 


61 



If a transformer has taps, connecting bigs, nuts and bars 
should be checked for missing parts. If they are missing, they 
will usually be found in the bottom of the case, where they were 
dropped while taps were being changed in the field. Spare con- 
necting links should be taped to leads. 



56 ELECTRICAL AIDS TO GREATER PRODUCTION 

It should be ascertained that coils and core are firmly held in 
place by the bolts and wedges. To send a transformer out loose 
in the case will often result in damage to coils and consequent 
breakdown. 

Testing for Burn-Outs. The most difficult of all repairs are 
those to coils. When a transformer comes in which is suspected 
of being burned out, unless it is evident from a superficial exami- 
nation that the coils are completely ruined, tests should be ap- 
plied with caution. A breakdown insulation test should never 
be applied until a megger is used. A premature insulation test 
may injure a transformer bej^ond repair. If the megger shows 
the insulation to be in bad condition, the transformer should be 
dried out by one of the usual methods and the test repeated. 
Such a dry-out will often correct the difficulty. Often a careful 
examination of the coils will reveal only a few damaged turns ; 
these may be replaced or reinsulated if carefully handled. If 
necessary, all coils should be disconnected so that each may be 
"meggered" to the core separately. The megger test is of course 
a preliminary step only for the purpose of trouble location. No 
transformer should be reinstalled which cannot withstand an 
appropriate insulation test. Ratio, core loss and exciting- 
current determinations should also be made on each transformer 
before it is considered ready. 

When it has finally been proved that a transformer is burned 
out it becomes necessary to decide upon its disposal. Several 
courses are open : It may be scrapped ; it may be returned to 
the manufacturer on some exchange proposition ; new coils may 
be wound in the local shop, or coils may be ordered from the 
manufacturer. In any case the decision will largely depend on 
the voltage class of the transformer, its age and type. Anti- 
quated types having operating characteristics inferior to those 
of modern transformers should seldom be rewound. Trans- 
formers of the 2300-volt class can usually be returned to manu- 
facturers for credit on a basis that is more economical than re- 
winding. On the other hand, it pays to order new factory-made 
coils for the higher-voltage classes. If a factory repair shop is 
available within reasonable distance, it may be cheaper to have 
the factory make complete repairs. When the coils are installed 
in a local shop, care must be taken to shellac and dry them thor- 
oughly. Some form of drying oven should be available, and the 



DISTRIBUTION, TRANSFORMATION, SWITCHING 57 

transformer should be placed therein at a temperature of about 
85 deg. C. (185 deg. Fahr.) for at least twenty-four hours. 

Transformers should be stored in such a manner that they will 
be easily accessible. If platforms rather than racks are used, 
ample aisles should be provided between rows to avoid breakage 
of bushings. Transformers of similar ratings should be 
grouped together. Burned-out transformers awaiting disposi- 
tion should not be mixed with the others, and to eliminate any 
chance of their being taken out by repair men in an emer- 
gency they should be given a dash of colored paint or otherwise 
conspicuously marked. 

Some recording system should be adopted in order that trans- 
formers returned from the lines shall be assured of proper atten- 
tion and that no transformer shall be taken out until it is in- 
spected and repaired if necessary. The three-part linen tag 
shown in Fig. 12 has been successfully used by one company for 
this purpose. Upon arrival the stock foreman issues a tag for 
each transformer. The lowest section is torn off and sent to the 
shop as a notification of work to be done; the remainder is at- 
tached to the transformer. When inspection, repairs and test 
are completed the middle section is torn off and sent to the rec- 
ord department as a notification of work done, and also that the 
transformer may be again placed on the active list. The upper 
portion of the tag remains attached to the transformer until it is 
reinstalled. The condition of each tag shows at all times the 
status of the transformer to which it is attached, and regardless 
of the method pursued in ordering out transformers for use, no 
transformer will be taken which has not received attention. 

SAFETY FEATURES IN SWITCHING INSTALLATIONS 

A great many ingenious and useful safety devices and schemes 
of connections have been devised within recent years, but the 
development of large-size and higher-voltage apparatus has been 
so overwhelmingly rapid that very often old and thoroughly 
experienced electrical engineers find it difficult to keep in touch 
with them. Even though the designing engineer is familiar with 
all of them, he may easily forget to include one or more essential 
safety features in his design. It is therefore the purpose of this 
article, by M. M. Samuels and F. N. Bechoff, not so much to 



58 ELECTRICAL AIDS TO GREATER PRODUCTION 

exhaust the whole field of safety engineering as to bring out in 
systematic form some of the well-known safety features and at 
the same time call attention to some which are less known but 
which are. nevertheless of great importance. It is hoped that 
other contributors will in the future make additional suggestions 
so that by and by the designing engineer as well as the operator 
will have ready references whenever he requires them. 

Types of Control Switches Desirable. The design of control 
switches is one of the first things that demand attention, since 
switching apparatus used in modern plants is usually installed 
remote from the switchboard and operated electrically therefrom 
by means of small control switches. To satisfy the majority of 
switchboard operators a control switch should be as easy to han- 
dle as possible and should be so constructed that the operator 
cannot perform the wrong operation. These requirements 
should be obvious, since it is very often necessary to open a 
circuit hurriedly without having any time for reflection. The 
switch should always be in working condition and ready to per- 
form safely the next operation. Poor contacts and hidden 
springs should therefore be eliminated. The usual method of 
indicating by means of colored lamps whether a circuit is open 
or closed is not sufficient for modern installations where it is 
possible not only for a circuit to open automatically but to be 
opened from other points either inside or outside of the power 
house. The lamp indicates only that the circuit breaker is open 
but does not indicate whether the circuit was opened by the 
operator himself. It is therefore essential that the control switch 
should be equipped with a reliable, prominent and easily distin- 
guishable mechanical indicator which will indicate the last opera- 
tion performed by the operator himself. There are some 
switches now on the market which meet these requirements. 

With the great number of indicating lamps on modern switch- 
boards, it is preferable in order to avoid confusion to have the 
two lamps of a control circuit together with the respective name- 
plates on a common escutcheon plate with the control switch. 
It should further be possible to lock the control switch so that 
it cannot be operated whenever any repairing or inspection is 
being done on the apparatus controlled by it. Push switches 
should not be used except in cases where they could not possibly 
be operated accidentally by the operator's elbow or knee. 



DISTRIBUTION, TRANSFORMATION, SWITCHING 59 

To avoid the possibility of closing a main generator circuit 
breaker without first going through the necessary process of syn- 
chronizing, it is customary to interlock the closing circuit of the 
circuit breaker with the synchronizing receptacle, so that the 



BELL 



CIRCUIT 
BREAKER 




HIGH-TENSION BUSES 



' POTENTIAL 
TRANSFORMER 



THREE -mY AUXILIARY 
SWITCH ON CIRCUIT BREAKER 



THREE-WAY PUSH-BUTTON 
SWITCH ON PANEL 



NO VOLTAGE 
RELAY - 



s\ RED LAMPLIGHTS 
\JWHENH.T.BUS 
_J IS ALIVE 



X. GREEN LAMPLIGHTS 
L) WHENH. T BUS 
IS DEAD 



110 VOLT \, C 



Figs. 13 and 14 — Three-way Auxiliary Push-button Interlocked with 
Three-way Auxiliary Switch for Resetting Bell Alarm; Method of 
Connecting Danger Signals Along a High-tension Bus 



HIGH-TENSION BUS 



HIGH- TENSION BUS 



DISCONNECTING 
SWITCH CLOSED 



DISCONNECTING SWITCH 
OPERATED BY MECHANISM 



> 



PF 



/ 



OIL CIRCUIT BREAKER 
OPEN 



%*. 



OIL 

CIRCUIT 

BREAKER 






fi c 



TRANSFORMER 



REDLAMP 

UOHTSWHEN 

DISCONNECTING' 

SWITCH 

IS CLOSED 



/rf 



OUTGOING 
LINE 



CONTACTS CLOSED WHEN 
DISCONNECTING SWITCH 
OPERATING LEVER IS 
IN CLOSED POSITION 

CONTACT CLOSED WHEN 
^- DISCONNECTING SWITCH 
OPERATING LEVER IS IN 
OPEN POSITION 

GREEN LAMPLIGHTS WHEN 
DISCONNECTING SWITCH 
IS OPEN 



I/O VOLT D. C BUSES 



Figs. 15 and 16 — Failure to Open Disconnecting Switch May Endan- 
ger Person Working Near Oil-switch Terminal ; Signals at Oil Switch 
Indicate Whether Disconnecting Switch is Open or Closed 



synchronizing plug must be inserted before the circuit breaker 
can be closed, as shown in Fig. 17. 

A system of control connections like that shown in Fig. 18 is 
still to be found in a good many installations. This method, al- 



60 ELECTRICAL AIDS TO GREATER PRODUCTION 

though it employs a small number of wires between the switch 
board and the circuit breaker, must be condemned from a safety 
point of view since it may happen, when a circuit breaker is 



1 10 VOLT D. C BATTERY BUSES 



D. C OPERATING BUS 



RED LAMP 







£V 



GREEN 
LAMP FOSE 



THIS CONTACT 
CLOSED WHEN 
CIRCUIT BREAKER 
IS CLOSED 

THIS CONTACT 
CLOSED WHEN 
| CIRCUIT BREAK- 
ER IS OPEN 

CLOSING 
COIL 



CLOSING 
.CONTACT 

CONTROL SWITCH 
ON SWITCHBOARD 
(Normally open) 

OPENING 
CONTACT 



CLOSED WHEN CIRCUIT 
BREAKER IS CLOSED 



I/O WLT D. C OPERATING BUS 




OH 



Od 



THESECONTACTSARE 
CLOSED WHEN 
CIRCUIT BREAKER 
IS CLOSED 

THESE CONTACTS 
ARE CLOSED WHEN 
CIRCUIT BREAKER 
IS OPEN 

CLOSING 

COIL 



RED LAMP LI6HTS WHEN 
CIRCUIT BREAKER 
IS CLOSED 

CONTROL SWITCH 

(Normally open) 



GREEN LAMP LIGHTS WHEN 

CIRCUIT BREAKER 

IS OPEN 

ft 



to 



110- VOLT DIRECT CURRENT OPERATING BUSES. 



Control Switch 
on Panel -----^ 



Red Lamp 

-®- 



7± 



Wl 



C/osi, ng Contact 



Open 



ing Contact 



£* 



■¥ 



rv\ 



Green Lamp 



Push Button Switch 
Normally open 



Closed when 
Field Switch /so/ 




Figs. 17, 18, 19, and 20 — Method of Interlocking Oil-Switch Control 
Circuit with Synchronizing Circuit; Three-wire and Four- wire Con- 
trol Circuits ( the Three-wire Arrangement has its Disadvantages ) ; 
Push-button in Field-control Circuit to Avoid Accidental Opening of 
Field 

being repaired, that an accidental short circuit across the green 
lamp, even with the control switch locked, would energize the 



DISTRIBUTION, TRANSFORMATION, SWITCHING 61 

closing coil and thus close the breaker and injure the operator. 
The scheme of connections shown in Fig. 19 is therefore to be 
recommended as far safer. The fact that with this scheme the 
red lamp is in series with the trip coil cannot be considered 
harmful, since a short circuit across the red lamp would only 
open the breaker. There is an additional advantage with this 
scheme, which is that any injury to the tripping circuit while the 
circuit breaker is closed will be called to the operator's attention 
on the switchboard by the automatic extinguishing of the red 
lamp. Thus the operator can always be certain that the tripping 
circuits is in good working order. 

Whenever a field circuit breaker of a large unit is electrically 
operated by means of a control switch care should be taken that 
the operator does not open the field accidentally or hastily. In 
order to force the operator to give the matter a second thought 
before opening the field it is advisable to insert a normally open 
push-button in series with the opening side of the control switch, 
so that to open the field both hands must be used. This arrange- 
ment is shown diagramatically in Fig. 20. 1 

All bell-alarm relays and other bell-operating devices should 
be so arranged that the bell continues ringing until stopped by 
the operator. However, whenever so stopped it should auto- 
matically reset itself and be ready for the next operation. A 
three-way auxiliary switch on the circuit breaker in connection 
with a three-way snap switch, as shown in Fig. 13, is often used 
for such purposes. The alarms for the various types of circuit 
breakers should be made distinguishable by using bells, horns or 
whistles having different sounds to indicate the automatic open- 
ing of different types of apparatus. 

The field switch for small units, mounted on the switchboard 
itself, should not be placed on the front but on the rear of the 
panel, with an insulated operating handle on the front to avoid 
accident through flashes. In this connection it may be suggested 
that it would be a great step toward safety if all lever switches, 
particularly those on 500-volt circuits, were similarly mounted 
on the rear of the panels. Carbon-break circuit breakers 
mounted on the front of the board should be so placed that they 
cannot strike a person standing near when they open automa- 
tically. Double-throw switches, if not mounted horizontally, 

- By courtesy of C. O. von Dannenberg. 



62 ELECTRICAL AIDS TO GREATER PRODUCTION 

should be equipped with locks or steps to prevent accidental 
closing. 

Fuses of heavy capacity should not be used at all, on account of 
their unreliability and also on account of the great maintenance 
expense, says Samuels. Automatic devices should be used in- 
stead. If fuses are used they should be of the inclosed type only 
and should be placed on the rear of the switchboard. 

Switchboards and Bus Compartments. Care should be taken 
to allow for liberal passageways behind all switchboards. A 
mistake is often made by providing a certain distance from the 
back of the panels to the wall without regard to the fact that 
many pieces of apparatus project a considerable distance to the 
rear of the board, thus materially reducing the size of the pas- 
sageway. The idea of insulating the switchboard frame must be 
considered altogether obsolete, and all switchboard framework 
should be grounded, this being by far the safer method. 

Whenever oil switches are mounted directly on the switchboard 
provision should be made to catch the oil in case of a leak in the 
tank in order to avoid oily and slippery floors around the switch- 
boards. Buses and connections within reach should be inclosed 
in grillwork, and in cases where a craneway exists over the 
switchboard protecting covering should also be installed above 
the switchboard to protect it from anything which may acci- 
dentally fall from the crane. 

Switchboard illumination is still a much neglected matter. 
For average switchboard heights 90-in. (228.6-cm.) shades, sim- 
ilar to Benjamin No. 5525, spaced approximately 5 ft. (1.5 m.) 
in front of board and 1 ft. (0.3 m.) above its top, will be found 
to give satisfactory results in most cases. 

All modern control switchboards should be equipped with 
mimic bars between all control switches to indicate the inter- 
connections between circuits. Such mimic bus arrangements 
should be made as simple as possible, and all control switches 
should be arranged with due regard to a simple layout of the 
mimic buses. 

A great deal of information on the subject of bus and oil 
circuit-breaker compartments was presented in the Electrical 
World of Jan. 15, 1916. If more attention had been paid to the 
suggestions made therein, some of the awkward bus arrangements 
which have recently come to the writer's attention could have 



DISTRIBUTION, TRANSFORMATION, SWITCHING 63 

been avoided. A few additional remarks on this subject will 
therefore not be ont of place. 

All openings in the bns structure opposite bus supports as well 
as those in front of bus section alizing switches should be closed, 
preferably by wire-glass doors, which will prevent accidental 
contact with live parts and at the same time allow for frequent 
inspection. Such doors should preferably be equipped with 
locks. 

The arrangement shown in Fig. 21 is to be preferred to that 
shown in Fig. 22 because the former allows complete inclosure of 
the buses without leaving any openings and at the same time 




Figs. 21 and 22 — Two Methods of Mounting Busbars, the First 

Being Preferable 



gives greater accessibility to the bars. It also makes it easier to 
arrange the bus laminations in vertical planes, which gives better 
cooling. In Fig. 22, where the insulator is mounted on the con- 
crete slab, the slab must be reinforced with iron, which is often 
the cause of heating, while in Fig. 21 no reinforcing is required. 
Compartment doors in front of oil circuit breakers or fuses 
should be so constructed that they can swing out in case of an 
explosion. On the other hand, doors in front of compartments 
containing apparatus not subject to explosion should be rigidly 
fastened. Hinged doors are to be preferred to removable doors, 
first, because the operator may forget to replace a removable 
door, thus leaving the compartment open; second, because a re- 
movable door is not adapted for locking, and, third, because a 
removable door if mounted at a considerable height may injure 
the operator while he is removing it. For compartments con- 



64 ELECTRICAL AIDS TO GREATER PRODUCTION 

taming apparatus of high rating the doors should be provided 
with openings for ventilation purposes. Hinged doors can be 
grounded, therefore there is no argument against the use of 
either all-metal or part-metal doors. In some stations the doors 
are so interlocked with the circuit-breaker mechanism that they 
cannot be opened unless the circuit breaker is open. This ar- 
rangement, although seemingly offering features of safety, has 
been found in many cases not to fulfill the requirements for 
which it was intended, since such interlocks are necessarily com- 
plicated and often prevent the door from being opened alto- 
gether when it is necessary to open it hurriedly. 

Generally it may be stated that the majority of oil circuit- 
breaker compartments are designed too small and are therefore 
inaccessible. Oil circuit breakers and mechanisms should be de- 
signed so that at least a 4-in. (10.1-cm.) brick wall can be built 
between phases and still leave ample handling space in the com- 
partments for wiring inspection, repairing and removal of the 
oil tanks, particularly for cases where a single oil tank is used 
for multiple circuit breakers. Even in cases where tank lifters 
are provided there is often hardly room enough for properly 
attaching the lifter to the tanks. 

For very long runs of busbars there should be lamps at certain 
intervals to indicate whether the bus is "alive" or not, a red 
lamp indicating danger and a green lamp indicating that the 
bus is "dead." A simple method for signals of this sort is 
shown in Fig. 14, where a potential transformer connected across 
the bus directly operates the red lamp, while the green lamp is 
supplied from an independent source of energy and is put in 
circuit by a no-voltage relay on the potential transformer. A 
green lamp alone would not give sufficient indication that the bus 
is dead, since an accidental interruption of the potential trans- 
former circuit, either through a short circuit in its winding or 
other causes, would cause the green lamp to light up even though 
the bus were alive. When both lamps are used the operator will 
know that the bus is "dead" only when the red lamp is out and 
the green lamp is on. In such cases potential transformers 
should be connected to the buses without fuses, as is done in the 
case of potential transformers on voltage regulators. 

Disconnecting Switches and Instrument Transformers. 
Where disconnecting switches are operated by switch hooks they 



DISTRIBUTION, TRANSFORMATION, SWITCHING 65 

should be equipped with locks to prevent their accidental open- 
ing. Such locks should be arranged so that the switch hook can- 
not be removed unless the switch is either entirely open or en- 
tirely closed and locked. However, it seems that the time is ripe 
for the complete elimination of the switch hook, which has ever 
been a source of danger to operator and apparatus. It is pos- 
sible to arrange disconnecting switches in such a way that they 
can be operated safely by means of a mechanism. 

Where disconnecting switches are mounted in compartments it 
should be possible to open the disconnecting switch before ope'n- 



Red and Green Lamp 
to indicate whether 
Oil Circuit-Breaker 
15 dosed or open ^j — 

Disconnecting 
Swirch... 



Auxiliary Switch 
closed when 
Disconnecting - 
Switches are 
closed^ 



Auxiliary Switch 
closed when 
Disconnecting 
Switches are 
open 



To Buses 



Red ana Green Lamps 
to indicate whether 
Disconnect ing-Switches 
are closed or .open 




Disconnecting ^ 
Sv 'itch s 

I; 

Fig. 23 — Proper Location of Red and Green Indicating Lamps on 
Switch Structure. Indicating Lamps Are Operated by Auxiliary 
Switches on Oil Circuit Breakers and Mechanically Operated Dis- 
connecting Switches 

ing the compartment door for reasons of safety. This, of course, 
is impossible when the switches are operated by means of a switch 
hook, but becomes feasible when the operation is performed by a 
mechanism, since an operating handle can be placed outside of 
the compartment. Switch hooks are often mislaid or eVen 
broken, and even when the switch hook is at hand it takes a 
considerable length of time to open six disconnecting switches, 
which must be done in the majority of cases to clear one circuit 
breaker. With a mechanism like in Fig. 23 1 all six disconnecting 
switches can be opened at once. 



i By courtesy of the J. G. White Engineering Corporation. 



66 ELECTRICAL AIDS TO GREATER PRODUCTION 

Where instrument transformers which are connected in series 
with oil circuit breakers have to be calibrated or repaired the 
operators sometimes open the oil switch, which of course "kills" 
the instrument transformer even if the disconnecting switch is 
closed (see Fig. 15). There are cases on record where an oper- 
ator, after finishing his work, in attempting to descend from the 
common foundation of the oil circuit breaker and instrument 
transformer, accidentally reached over to the live side of the oil 
circuit breaker and was killed. For this reason it might be 
advisable to have a warning signal at the oil circuit breaker to 
tell the operator that the disconnecting switch is closed. Such a 
signal cannot be prodded easily where disconnecting switches 
are operated by switch hooks. However, where the disconnecting 
switches are operated by some mechanism it is a very simple 
matter to install an auxiliary switch which would light 
a red lamp at the oil circuit breaker when the disconnecting 
switch is closed and a green lamp when it is open (see Fig. 24). 
Such auxiliary switches can also operate red and green lamps on 
the switchboard panels in similar manner. 

As an additional precaution, a multi-tumbler lock might be 
installed on the disconnecting switch handle to lock it in the 
closed position, so that nobody could accidentally open the dis- 
connecting switch under load. It could also be locked in the 
open position, so that nobody could close the disconnecting switch 
when repairing or inspection is being done on the oil circuit 
breaker. Of course, better results could be obtained with elec- 
trically operated disconnecting switches, either by motor or sole- 
noid, and where the extra expense is warranted electrical opera- 
tion from the switchboard should be used. With this arrange- 
ment it is, of course, possible to go a step further and interlock 
the control circuits of the oil circuit breaker and the disconnect- 
ing switches. 

Disconnecting switches should be so placed that the blade is 
dead when the switch is open. This is not always possible when 
using hook-operated switches but is possible in every case when 
the disconnecting switches are operated by a mechanism as shown 
in Fig. 23. 

Best Locations for Pilot Lamps. In order to remove as much 
uncertainty as possible regarding the open or closed condition of 
oil switches and disconnecting switches when they or their re- 



PI 




C3 




r£ 


• 


o 


e 


01 


0) 


s 


o 


^ 


(/} 


rO 


• I-H 







68 ELECTRICAL AIDS TO GREATER PRODUCTION 

spective circuits must be inspected or repaired, indicating lamps 
can be permanently placed at the points from which they are 
controlled and at the switch positions too. This is not imprac- 
ticable if the disconnecting switches are operated by mechanical 
devices instead of hook switches and are provided with auxiliary 
switches to control the indicating lamps. 

An arrangement which will suggest how this idea can be car- 
ried out is shown in Fig. 24, desirable locations for the pilot 
lamps being indicated in Fig. 23. This scheme can be employed 
with outdoor open structures as well as with indoor compartment 
structures. 

It is not advisable to use exposed colored bulbs for the pilot 
lamps, since they are easily damaged and since an operator when 
renewing lamps might accidentally place a green bulb in a socket 
intended for a red bulb and vice versa. White bulbs installed 
in a metal box with red and green lenses in the cover are prefer- 
able ; the cover should be constructed in such a way that the red 
and green lenses cannot be interchanged. Details of a box, with 
lamps and lenses, which fulfills these requirements and allows 
ample space for the necessary conduit connection and wiring are 
shown in Figs. 28, 29 and 30. A barrier is provided between the 
two bulbs so that they can illuminate only their respective lenses. 
To identify the circuits a name plate can be affixed to the cover. 

Possibility and Value of Interlocking Control Apparatus. 
hi addition to providing for the interlocking of oil-circuit- 
breaker control and synchronizing circuits, it is possible, when 
using mechanically operated disconnecting switches, so to inter- 
lock the control circuit with the mechanism of the disconnecting 
switch that it is impossible to close the oil circuit breaker unless 
the disconnecting switch has previously been closed. A method 
of securing this desirable feature is indicated in Fig. 25. 

Even if indicating lamps are used, it may happen that an 
operator, after having adjusted the speed of a generator to se- 
cure synchronism, will close the oil circuit breaker, only to dis- 
cover that the disconnecting switches are still open. If an oper- 
ator were sent to close the disconnecting switches and he acci- 
dentally did so before the other operator reopened the oil cir- 
cuit breaker, serious damage might result as a generator would 
then be connected to a bus with which it was not in synchronism. 

When disconnecting switches are used as bus-selector switches 



•2 "5 -s 

t; ^ £ 
1 £ * 



2 .&{ 



•S .5" 



1 1 

P o 

G 

S3 ui 



s s ^ 

V) ^ ^ 

•« "S "§ 

'5 £ SO 

§ ,-5 ,-9 

•^ O O 



£b* 



t s: 

tit 

III 



m 



x 



*3 









^ C><5^ 



I 





IPS 

5; g-^cn 



< 




P 'PH .PH 


02 




a <u £ 


fk 




o^v 


< 




Coo 




° 'S 2 

o !> C 






ai (0 O 


h5 

< 




3 >>" 


EH 

O 


^ Cj h 


o 


O 1= c3 


Ul 




O i> CQ 
^ g PL, 

o e3 S 


h- 1 

O 

H 


o 

02 
fa 
3 




X 


03 — CU 
!h C ^- 


«/> -1 


W 


0) co fcx) 


-3 w 
dL >-* 

-I £ 

O 

Q 


H 
O 

pq 

o 
a 
i 


O g O 

^ fl fl 
" CO ^ 

§ a 2 


<i 


u 

fa 


i o o 
S c « 


02 


fe 


M 


fe 


<J 


o 




M 


u 


^ .m OJ 


02 


r/) 


P! - rC 




^H 


« .~S u 


H 








<D O ? 


fa 




rf'2 » 


o 




O pG t 




M 


^ rj OS 

go !J3 ^5 


02 


fa 


H 
fa 


p 

fa 
DQ 


O 


c| co as 

" ^2 o 




w 


S - -fl 




H 


P P +a 
« ° n 


fa 


| 


<u ^ 2? 

J 8 J 


fa 


fa 


H fet 


m 


M 
H 


'P. "^ ^ 


H 

M 


£ 


p 

GC 


fa 


CO «4H .JT 1 

P O -+J 




-4 


o ^ 


w 


U 


•Pi bJD P 


fe 


H 

Q 


o.s a 


o 

M 

H 


fc 

h— 




Q 

fa 


o 




fe 


M 


bfi co " 


O 


fa 


P -^ 2 


O 

C5 


3 
M 
O 


•^ P Pi 

N S P 

S r» O 
M O) O 


K 


fa 


P 5i 


M 


m 


pP ^ Jh 


N 


ft 


M 

o 


< 
H 


o CS 




H 


bD P 

.p^pI 


§ J- 
►5 N 


< 


P -rJ 


M 

w 

a 

H 

w 


S4H "- 1 <D 

° * IT 

flo.5 

•f3 PH -P 


Q 




^ M Cj 


< 




o co £ 


CO 




ft M ° 
HH 'S <N CO 


02 




^ • .2 


O 




t &Ch 


i-i 




F^ 




02 HH CO 



69 



70 ELECTRICAL AIDS TO GREATER PRODUCTION 

it may happen, when attempting to synchronize two systems, 
that the wrong disconnecting switch will be closed. If this 
condition exists and the operator closes the oil switch after 
apparently synchronizing the two circuits he expects to connect, 
two buses will be connected which may be entirely out of phase. 
This would not be liable to happen with mechanically operated 
disconnecting switches having pilot lamps on the board from 
which the oil switches are controlled. Absolute safety would be 
assured if the disconnecting switches, circuit breaker and syn- 
chronizing plug were electrically interlocked so that the circuit 
breaker could not be closed unless the disconnecting switch cor- 
responding to the position in which the synchronizing plug was 
placed were closed (Fig. 26). 



Green 
Lens 



Hinge 



Name Plate'' 




Colored 
Lens- 



Ventilating 
Openings 

Cover 



Barrier 



1 




RED 



~T T 

-Hole ■ 
■For Leads 



-J 



SECTION 
HROUGH BOX 



mi MM — 

VIEW OF BOX WITH 
COVER REMOVED 



_1 



Figs. 28, 29 and 30 — Signal Box for Red and Geeen Indicating Lamps 
on Switch Structures ; Barrier Prevents One Lamp from Illuminating 
Both Lenses; Unsymmetrical Hinged Cover Prevents Interchange- 
ability of Colors 



Some liability insurance companies now require that red and 
green lamps be placed near each transformer of high rating or 
high voltage and so connected that the red lamp will indicate 
when the switch on either the high-tension or the low-tension side 
of the transformer is closed and that the green lamp will indi- 
cate when both the high-tension and low-tension switches are 
open. This can be accomplished very easily with the connection 
shown in Fig. 27. The two auxiliary switches controlling the red 
lamps are connected in multiple, while the two auxiliary switches 
controlling the green lamps are in series. Where each trans- 
former is installed in a separate compartment it is advisable to 
provide signal lamps (Fig. 28) ouside of the compartment near 
the door. 

Protecting Main Transformers. All modern high-rated trans- 
formers are now equipped with dial thermometers, which indicate 



DISTRIBUTION, TRANSFORMATION, SWITCHING 71 

the transformer temperature. Some have a contact to ring a 
bell alarm when the temperature exceeds a given limit. A sec- 
ond contact may be attached to such thermometers in order to 
trip the transformer oil circuit breaker when the temperature 
rises above a certain limit. This is particularly advisable when 
a transformer is placed far enough from the operator to cause 
danger of the transformer burning out in the interval of time 
between receiving an alarm and reaching the transformer. 



THERMOMETER 
WITH ALARM CONTACT , 



First Contact to operate 
Bell Relay and Red Light "A" 

. - -Second Contact to 



Trip Oil Circuit-Breaker 




Red Lamp- 
"A" 



1IO-VOLT OPERA TING BUSES 

%Bell 
Bell Relay 
Bel I A/arm Bus 




r- 



Emergency Switch Normally 
t<- open to Trip Oil Circuit-Breaker 

±1 



Red Lamp -:y~N 

*£ 

Opening £_ 4 

Lonta 



Contact to operate 
Bell and Red Light'A" 
■when Flow, of mrter 
is interrup ted 



Contact closed when 
Oil Circuit-Breaker — ' 
is closed 



Oil Circuit-Breaker ■-> 



ntact-> 



Green 
Lamp 




Control 
Closing 
Switch 



Closing 
Coil 



Fig. 



Closed when Oil Circuit-Breaker 
is open 

31 — Temperature and Water-flow Alarm Connections for Trans- 
former 

An additional contact is provTcTecTon the transformer temperature alarm 
for tripping the circuit breakers at excessive temperatures; an emergency 
tripping switch is also provided at the transformer. 



Where the transformer is so situated means should also be pro- 
vided for the operator to trip the circuit breaker from a point 
near the transformer if an occasion should arise making it neces- 
sary. A scheme which will provide such safety features is illus- 
trated in Fig. 31. 

Usually water-cooled transformers are equipped with flow in- 
dicators which can be electrically connected with the tempera- 
ture indicator alarm circuit so that interruption of water circu- 
lation will automatically give an alarm. When thermometers 
are used in connection with transformers they should be so in- 
stalled that it will not be necessary for an operator to climb a 



72 ELECTRICAL AIDS TO GREATER PRODUCTION 

ladder in order to read the temperature. Use of contact-making 
thermometers will eliminate this objection. 

Weaknesses of Auxiliary Switches and Relays. Up to the 
present time, in Samuels' and Bechoff's opinions, there has not 
been developed an auxiliary switch for oil circuit breakers and 
other apparatus which is adequate for all purposes. Considering 
the fact that the operation of nearly all safety devices in power 
houses and substations depends chiefly on the proper and reliable 
operation of auxiliary switches, it is obvious that even with 
modern indicating and automatic safety devices there cannot be 

110- VOLT DIRECT CURRENT 0RERATIN6 BUSES AT SWITCHBOARD 



Control Switch 
operates Starting 
ana" magnetizing 
Oil Circuit -Breaker 
m Parallel 



Starting and magnetizing Q ^ 
Oi I Circuit Breaker Lamp 



Red Lamp 

'"©-1 

Closing. 

. 32 

Open ing 



Red Lamp 



Control ■ 
Switches 



[For 



-/ C,osin 9 Contact running 

*■ — * -> ■ n . .1 Oil Circuit 

Open,ngContact\ Breaker 



Green Lamp 




Running Oil 
Circuit Breaker 

0=Aux Switch closed 
when Oil Circuit - 
Breaker is open 

C - Aux Switch closed 
when Oil Circuit - 
Breaker is closed 



-x 



Closing Ceil of running 
Oil Circuit -Breaker 



BREAKERS 



Fig. 32 — System of Connections for Interlocking Starting, Magnet- 
izing and Kunning Switches of Large Motors ; Proper Operation of In- 
terlocking Connections Depends on Reliability of Auxiliary Switches 



a high degree of safety unless a standardized, practically infal- 
lible auxiliary switch is developed. Auxiliary switches which 
may have been perfectly satisfactory for apparatus used in the 
past are not at all adequate for modern circuit breakers because 
their rupturing capacities and velocities of operation have both 
been increased. All auxiliary switches should be easily acces- 
sible for connection, inspection and repair. Owing to unreli- 
ability of auxiliary switches known to the authors, it is some- 
times necessary to use multiple contacts, but this precaution does 
not always prevent auxiliary switch trouble. Usually there is an 
auxiliary switch in the tripping circuit of each circuit breaker, 



DISTRIBUTION, TRANSFORMATION, SWITCHING 73 

and if this switch fails the circuit breaker will fail to open when 
overloaded or short-circuited, thus causing considerable damage 
to the transformers and other apparatus connected therewith. 

The interlocking of circuit breakers to prevent the simultane- 
ous closing of two or more of them where such simultaneous clos- 
ing would be dangerous is usually accomplished by auxiliary 
switches. For instance, when large motors are started by means 
of a compensator a magnetizing switch, a starting switch and a 
running switch are provided. It is important that the control 
circuits of these three switches be interlocked so that the running 
switch cannot be thrown in until the motor is brought to speed 
by the magnetizing and starting switches. It is of even greater 
importance not to have the starting and running switches both 
closed at the same time, since under this condition the compen- 
sator would burn out. Interlocking to prevent such trouble may 
be accomplished with hand-operated switches by mechanical 
means, but with electrically operated oil circuit breakers it is 
necessary to interlock the control circuits electrically by means 
of auxiliary switches unless the control switches are mechan- 
ically interlocked. Although interlocking of the control circuits 
gives a more flexible arrangement, it cannot be considered the 
safest method unless a thoroughly reliable auxiliary switch is 
employed. The connections for electrically interlocking oil cir- 
cuit breakers used in starting either synchronous or induction 
motors are shown in Fig. 32. 

What applies to auxiliary switches is likewise true of relay 
contacts. Although progress has been made in the design of 
various types of relays, their contacts should be further im- 
proved, since the majority of modern relay contacts are unable 
to carry the current required to trip large circuit breakers. 
Often it becomes necessary to resort to auxiliary relays, which 
are only an additional evil, because the size of nearly all relays 
is restricted by the secondary ampere rating of the current trans- 
formers, which generally does not exceed 5 amp. White 5-amp. 
secondaries are sufficient on current transformers for use with 
meters and also for operating automatic devices on circuits of 
low capacity, they are hardly suitable for oil circuit breakers of 
high rupturing capacity. Therefore it is suggested that the sec- 
ondary rating of current transformers for such protective pur- 
poses be increased. When this is done it will be possible to 



74 ELECTRICAL AIDS TO GREATER PRODUCTION 

develop relays with contacts of adequate size. While the same 
current transformer is suitable for both the meters and relays in 
small installations, two separate sets of current transformers are 
advisable in large installations: One set should be used for the 
meters and the other for automatic relay protection. With this 
arrangement it is obvious that an increase in the rating of the 
secondaries of the relay current transformers would not destroy 
the accuracy of the meter reading, a consideration of importance. 

It is still customary to install all relays on the switchboard, 
this arrangement being necessary because the present relays re- 
quire constant attention and frequent inspection and adjustment. 
With current transformers having a higher secondary rating it 
will be possible to design relays of large sizes and more rugged 
construction. Such relays would not have to be mounted on the 
switchboard but could be placed near the oil circuit breakers or 
other apparatus which they are to protect, thus eliminating un- 
necessary conduits and wiring and minimizing the switchboard 
space necessary. 

Provisions should be made for disconnecting control devices 
from the control bus to permit repairing and inspection. 

Bell Alarms. Since the major portion of the switching appa- 
ratus in large plants is usually installed remote from the switch- 
board, so that the switchboard operator is not in a position to 
observe the automatic tripping of circuit breakers or the exces- 
sive heating of transformers and other apparatus, it is necessary 
to provide some form of alarm for this purpose. In spite of the 
obvious importance of such alarms the subject has hardly ever 
been discussed in engineering literature, and a great deal of con- 
fusion and misconception with reference thereto exists in the 
minds even of some good designers and operators. It is the 
authors' intention to give first a brief review of the existing 
methods of alarm, then discuss their weak points and make sug- 
gestions for improvements. 

The fundamental requirement of any alarm is that it must be 
self-resetting. In other words, when the apparatus which 
caused the alarm is again placed in normal operation the alarm- 
giving device should automatically be ready to give an alarm if 
trouble recurs. 

Alarms for Hand-Operated Circuit Breakers. — For hand-op- 
erated circuit breakers having lever switches in series with them, 



DISTRIBUTION, TRANSFORMATION, SWITCHING 75 

the connections can be arranged as in Fig. 33. With this method 
auxiliary contacts are provided on the circuit breaker as well as 
on the lever switch, both the auxiliary switches being in series 
with a bell circuit. The auxiliary switch on the circuit breaker 




LEVER - 
SWITCH 



BUS 



"Auxiliary switch 
closed when circuit 
breaker is open 



. - Auxiliary switch 
open when lever 
\ switch is open 



Position Position 
No.1 No.2 



Position 
No. 3 



(~\BEU 



¥ 



-=- BATTERY, 



T 



Position No.l Circuit in working condition 

Position No. 2 Circuit breaker opened automatically Bell is ringing 

Position No 3 Operator opened lever switch which stopped bell 



eh closed when 
circuit brez ker is closed 

circuit 




Position Position Position Position 
No.iondNo.5 No.2 No.3 No. 4 



Position No. I Circuit in working condition 

Position No.2 Circuit opened automatically Auxiliary switch starts bell 

Position No.3 Operator brings three way push button from 3 to A thus stopping the bell 

Position No.4 Circuit breaker closed again Bellrings 

Position No. 5 Operator brings three way push button back from A to B 

thus stopping bell and resetting it for next tripping 

of circuit breaker 

Figs. 33 and 34 — Circuit Breakers With and Without Lever Switch 

in series 



is open when the circuit breaker is closed and is closed when the 
circuit breaker is open, while the auxiliary switch actuated by 
the lever switch is closed when the lever switch is closed and is 
open when the lever is open. Thus when the breaker trips auto- 
matically it closes the bell circuit, as shown in position 2 of Fig. 



76 ELECTRICAL AIDS TO GREATER PRODUCTION 

33, thereby ringing the bell. The operator may interrupt the 
ringing of the bell by opening the lever switch as shown in posi- 
tion 3 of Fig. 33. When the lever switch is closed after reclosing 
the breaker the bell circuit is made automatically ready to give 
an alarm if the breaker trips again. 

For circuit breakers not having lever switches in series with 
them the problem becomes a little more difficult. In order to 
provide automatic resetting of the bell circuit it is necessary to 
equip the circuit breaker with a double-pole auxiliary switch, one 
side of which is closed when the circuit breaker is closed and 
the other side closed when the circuit breaker is open. Such an 
auxiliary switch is called a "circuit closing and opening auxil- 
iary switch." In addition to this it is necessary to provide on 
the switchboard a three-way snap or push switch for each circuit 
breaker, as shown in Fig. 34, the diagram being self-explanatory. 
With this arrangement the resetting of the bell circuit is not 
automatic but must be done by the operator. In order to re- 
mind the operator to reset the three-way push-button, the circuit 
breaker rings the bell when it closes and the ringing is only 
stopped when the operator resets the button. 

Alarms for Electrically Operated Circuit Breakers. Of far 
greater importance is the bell-alarm indication for electrically 
operated circuit breakers. Such circuit breakers are always 
placed at a considerable distance from the switchboard. Auto 
matic electrically operated circuit breakers are tripped by means 
of overload reverse-energy or other types of relays. Such re- 
lays are always deenergized the moment the breaker opens, and 
if the bell alarm were operated directly by the overload relay 
the bell would only ring for a very short period and might stop 
ringing before the operator heard it. 

To avoid this objection a special type of relay has been devel- 
oped which is so constructed that the contacts which close the 
bell circuit stay closed even after the circuit of its coil is inter- 
rupted. Thus the bell should continue ringing until stopped by 
the operator. Such relays are commonly known as "bell-alarm 
relays. ' ' Figs. 35 and 36 show the connections of two of the best- 
known bell-alarm relays. The type shown in Fig. 35 is so con- 
structed that the core which closes the bell circuit contacts stays 
up after it is once raised by the coil, even after the coil circuit 
is broken. In order to interrupt the bell circuit it is necessary 



DISTRIBUTION, TRANSFORMATION, SWITCHING 77 



for the operator to pull the core down by hand, which can be 
done by means of a knob at the bottom of the relay. This 
relay must, of course, be mounted within easy reach of the 
operator. With the relay shown in Fig. 36 the ringing of the 



BUS 



CONTROL 
RELAY.. 



D. C. OPERATING BUSES 



FED LAMP 

<5H 



Cbsinq^- 



e 



AUXILIARY 
SWITCH 



] ' n 3 , 



2L, 



-®-J 



CONTROL 
SWITCH 



CLOSING 
COIL 



'"Pi 

\TRIP 
COIL 



GREEN LAMP 




BELL 



OIL CIRCUIT BREAKER 

(SOLENOID OPERATED) 



n 



BELL ALARM RELAY 
RESET BUTTON 



RELAY BUS 



CURRENT TRANSFORMER 



OVERLOAD RELAY 



A = Closed when Oil C B is-closed 
B = Closed when Oij C. B. Is open 



DC OPERATING BUSES 




Figs. 35 and 36 — Bell Relay Mechanically and Electrically Reset 



bell is maintained by means of an auxiliary coil having common 
yoke with the main relay coil ; interruption of the bell circuit is 
accomplished by means of a normally closed momentary push- 
button on the switchboard. It would not be practicable to pro- 



78 ELECTRICAL AIDS TO GREATER PRODUCTION 

vide a separate bell and a separate bell relay for every auto- 
matic circuit breaker ; therefore it is customary to make one bell 
relay with its bells serve for a great many circuit breakers. 



BUS 



BREAKER J) 



CIRCUIT 



^W9 



AUXIUARr . 

SWITCH- 
W/THPASSIN6 

CONTACTS 



BELL 
RELAY. 




BELL 



Position Position Position 
No. I No. 2 No. 3 

Position No. I Circuit in operating condition 

Position No.2 Circuit breaker just opening energizing 
t>ell relay by auxiliary switch passing contact 

Position No. 3 Circuit breaker all open Bell relay not 
energized but bell relay contacts still 
closed Bell circuit can now be broken 
by resetting bell relay 



Fig. 37 — Auxiliary Switch Operates Bell Alarm 




BUS 




A = Closed when oil circuit breaker is closed 
B = Closed when oil circuit breaker is open 

Fig. 38 — Trip Coil in Series with Bell Alarm 






This is accomplished by means of a bell relay bus, as shown in 
Fig. 38. 

Upon carefully analyzing the connection shown in Fig. 38, 
which exists in practically every power house or substation using 
electrically operated circuit breakers, the most startling discov- 



DISTRIBUTION, TRANSFORMATION, SWITCHING 79 

ery is made that every trip coil on the system is in series with 
the one bell-alarm relay coil. This means that if the one bell- 
alarm relay coil should be out of service it would not be possible 
for any circuit breaker to open under overload, short circuit or 
reverse energy, thus subjecting the whole system to disaster. 




Fig. 39 — Tripping Circuit Independent of Bell Alarm 



£ 



(SU RED LAMP 

control ry 



SWITCH 



Vr 




OPERATING BUSES 



ANNUNCIATOR PANEL .. 



THERMOMETER 
n CONTACTS. 

ANNUNCIATOR 

DROPS : 

=MrT 



TRANSFORMERS 



BELL RELAY BUS 



TTT 



.PASSING CONTACT 
AUXILIARY SWITCH 



CARBON CIRCUIT BREAKER 



Fig. 40 — Connections for Annunciator Making Trip Coils Independent 

of Alarm 



Even though the bell-alarm relay is of very simple construction 
and not subject to great abuse, the possibility of an interruption 
is always present. It seems to be due to good fortune only that 
one does not often hear of station troubles caused by the failure 



80 ELECTRICAL AIDS TO GREATER PRODUCTION 

of a bell-relay coil. It is possible that many station disasters 
in the past, the cause of which could not be traced, were in reality 
due to an interruption of a bell-relay circuit. A partial remedy 
can be obtained by the use of two bell relays in multiple, which 
method is now being employed in some cases. But it must be 
admitted that such a remedy is only a palliative and does not go 
to the root of the evil. 

Safe Method That Future Will Demand. The only safe 
method to be employed in the future and to be favored by insur- 
ance companies is to make the automatic tripping of the circuit 
breaker entirely independent of the bell-relay coil. In order to 
accomplish this it is suggested that there be provided on every 
electrically operated circuit breaker a "passing contact auxiliary 
switch," which should be so constructed that it is actuated me- 
chanically by the opening mechanism of the circuit breaker. 
This auxiliary switch should be so arranged that it closes only 
momentarily during the opening period of the circuit breaker. 
This short period would be sufficient to energize a bell relay, the 
contacts of which would stay closed even after the "passing con- 
tact auxiliary switch" is open and thus would continue to ring 
the bell until the operator resets the bell relay. A diagram 
showing the simplest form of this arrangement is given in Fig. 
39, which is self-explanatory. With the scheme shown in Fig. 39 
the bell would also ring when the circuit is opened by hand. 
Instead of being a disadvantage this should be considered an 
advantage, because the operator who is not in the same room 
with the circuit breaker, when hearing the bell will know defi- 
nitely that the circuit breaker actually opened. If so desired, 
this same auxiliary switch in its simplest form would also ring 
the bell when the circuit is being closed, which would be a defi- 
nite indication for the operator that the switch is actually closed, 
even when the red lamp is burnt out. For remote-control hand 
mechanisms, which generally have no indicating lamps, the ring- 
ing of the bell when the operator closes or opens a circuit breaker 
would be of still greater importance. If the ringing feature is 
not desired when closing the circuit breaker it can be easily elimi- 
nated by a suitable design of the "passing constant auxiliary 
switch. ' ' By referring to Fig. 39 it will be seen at once that the 
tripping circuit has no connection whatever with the bell-alarm 
relay, so that an injury to the bell-relay coil circuit will not 



DISTRIBUTION, TRANSFORMATION, SWITCHING 81 

endanger the tripping of the circuit breaker under overload. 
The "passing constant auxiliary switch" can also be applied 
to hand-operated circuit breakers, as shown in Fig. 37. This 
arrangement would eliminate the necessity of installing a three- 
way push-button for every circuit breaker, as described before 
in connection with Fig. 34. 



ALLOWABLE SIZES OF WIRE FOR INTERMITTENT 

LOADS 

The ultimate temperature rise of a conductor subject to a 
given intermittent load depends upon the ratio of the "on" 
and "off" time of the current. Unless the current is off long 
enough to allow of the dissipation of all of the heat accumulated 
during the "on" period, the temperature will rise. At low 
temperatures the dissipation of heat proceeds at a very slow rate, 
but at the higher temperatures such as 20 deg. or 30 deg. C. it is 
quite rapid. Therefore the relative time in which a given quan- 
tity of heat may be dissipated varies greatly with the tempera- 
ture rise permitted. These facts are illustrated in Tables III 
to XVIII inclusive, which are designed to assist in selecting the 
smallest wire that may be used to carry a given intermittent 
load. These tables refer only to wire in conduit and are based on 
extensive tests conducted by H. C. Horstman and Victor Tousley. 
The data are not presented to discountenance the National Elec- 
tric Code rulings regarding wire sizes but they do indicate that 
much smaller conductors can be used with intermittent loads than 
are now required. 

Explanation of the Tables. A separate table is provided for 
each of the wire sizes considered, and each table has two parts. 
In the left-hand portion of the tables is given the time in seconds 
required, for the various currents in amperes given at the top, 
to raise the temperature of the conductor 2 deg. above the sur- 
rounding air within the range of temperature given at the ex- 
treme left. Thus, referring to No. 14 wire, 20 amp. will raise 
the temperature of the conductor from 10 deg. to 12 deg. C. in 
120 seconds, but it will require 420 seconds to effect a tempera- 
ture rise from 20 deg. to 22 deg. In the last columns at the 



82 ELECTRICAL AIDS TO GREATER PRODUCTION 



Time in Seconds Required to Raise or Lower Temperature 



TABLE Ill- 
Temperature 
Range, deg. C. 
10-12 . . 


-THREE NO 
EK 

f 
15 

690 


14 D. B. 
"AMELED 

—Heating 
20 

120 
130 
180 
240 
300 
420 
570 
1,500 

12 D. B. 
AMELED 

—Heating 
25 

105 
135 
165 
225 
330 
405 
560 
1,860 

10 D. B. 
AMELED 

—Heating 
35 

120 
135 
150 
165 
18-0 
240 
300 
400 
780 


R. C. WIRES IN y 2 
CONDUIT 

Load, Amp. , 

25 45 

60 12 

65 12 

70 12 

75 12 

80 12 

90 12 

100 12 

110 12 

125 12 

R. C. WIRES IN % 
CONDUIT 


-IN. BLA( 

Cooling 
(Am] 
7% 
330 
350 
180 
135 
120 
105 

85 

75 

60 

■IN. BLA( 

Cooling 
(Am] 
10 

195 
18-5 
135 
115 
100 

90 

80 

70 

70 

IN. BLAC 

Cooling 
(Amj 

i2y 2 

390 
300 
210 
180 
150 
120 

90 

80 

60 


Load 

P.) 


180 


12-14 . . 


1,200 


135 


14-16 . . 


2.400 


120 


16-18 . . 




105 


18-20 . . 




90 


20-22 . . 




75 


22-24 . . 




60 


24-26 . . 




60 


26-28 . . 




55 


TABLE IV- 

Temperature 
Range, deg. C. 
10-12 .. 


-THREE NO. 
ES 

r 
20 

330 


:k- 

Load 

T 1 


35 

48 
48 
48 
48 
48 
48 
48 
48 

R. C. WIRES 
CONDUIT 


60 
10 
10 
10 
10 
10 
10 
10 
10 

IN %■ 


M 



160 


12-14 . . 


480 


125 


14-16 . . 


840 


115 


16-18 . . 


1,920 


95 


18-20 . . 
20-22 . . 




90 

80 


22-24 . . 




70 


24-26 . . 




70 


26-28 . . . 




70 


TABLE V— 

Temperature 
Range, deg. C. 
10-12 . . 


-THREE NO. 
EN 

r 
25 

440 


Load 


50 

50 
50 
50 
50 
50 
50 
50 
50 
50 


75 
15 
15 
15 
15 
15 
15 
15 
15 
15 



225 


12-14 . . 


720 


210 


14-16 . . 


1,500 


180 


16-18 . . 




150 


18-20 . . 




120 


20-22 . . 




100 


22-24 . . 




90 


24-26 . . 




80 


26-28 . . 




60 



DISTRIBUTION, TRANSFORMATION, SWITCHING 83 



Time in Seconds Required to Raise or Lower Temperature 

(Continued) 



TABLE VI— THREE NO. 


8 D. B. 


R. C. WIRES IN 


1-IN. BLACK- 




ENAMELED 


CONDUIT 


















Cooling 


Load 


Temperature 


r 


-Heating 


T,nQn A tyi T\ 




(Am 


n ~k 


XjOdtlj xaIUJJ. 


^ 


}•) 


Range, deg. C. 


35 


50 


70 


105 


ny 2 





10-12 


510 


120 
135 
165 


43 
43 
43 


16 
16 
16 


540 
405 
320 


465 


12-14 


790 


3.70 
240 


14-16 


1,600 


16-18 




180 
210 
240 
300 
350 
510 


43 
43 
43 
43 
43 
43 


16 
16 
16 
16 
16 
16 


270 
215 
180 
150 
100 
90 


195 


18-20 . 




140 


20-22 




125 


22-24 




105 


24-26 




100 


26-28 




90 


TABLE VII— THREE NO 


6 D. B. 


R. C. WIRES IN 


1-IN. BLACK- 




ENAMELED 


CONDUIT 


















Cooling 


Load 


Temperature 




rTo Q "f" 1 Tl O 


Load, Amp — 




> (Am] 


-> \ 


( 


■Tied Llllg 




3.) 


Range, deg. C. 


50 


70 


80 100 


150 


25 





10-12 


. 420 


105 


75 37 


14 


750 


300 


12-14 


. 630 


120 


80 37 


14 


510 


260 


14-16 


. 900 


140 


80 37 


14 


390 


225 


16-18 


. 1,560 


150 


80 37 


14 


300 


190 


18-20 




160 


80 37 


14 


240 


175 


20-22 




180 


90 37 


14 


185 


160 


22-24 




200 


105 37 


14 


160 


135 


24-26 




210 


110 37 


14 


125 


120 


26-28 




240 


125 37 


14 


100 


100 



TABLE VIII— THREE NO. 4 D. B. R. C. WIRES IN 1*4 -IN. BLACK- 
ENAMELED CONDUIT 



Temperature 
Range, deg. C. 


70 


Heating Load, Amp 

80 90 100 


140 


210 


Cooling Load 
(Amp.) 
35 


10-12 


.. 310 


225 


135 


120 


40 


17 


900 


350 


12-14 


.. 400 


250 


150 


120 


40 


17 


600 


250 


14-16 


.. 500 


280 


175 


120 


40 


17 


420 


220 


16-18 


.. 700 


320 


200 


130 


40 


17 


360 


200 


18-20 


.. 900 


390 


225 


135 


40 


17 


300 


180 


20-22 


. . 1,200 


450 


240 


140 


40 


17 


240 


150 


22-24 


. . ... 


540 


275 


150 


40 


17 


190 


120 


24-26 


. . ... 


840 


375 


180 


40 


17 


160 


90 


26-28 





2,100 


420 


215 


40 


17 


150 


75 



84 ELECTRICAL AIDS TO GREATER PRODUCTION 

Time in Seconds Required to Raise or Lower Temperature 

(Continued) 

TABLE IV— THREE NO. 3 D. B. R. C. CABLES IN iy 2 -IN. BLACK- 
ENAMELED CONDUIT 



Temperature 
Range, deg. C. 




TTni 4~ i x\ f 


l Load, Amp — 
100 160 




Cooling 
(Am 
40 


Load 

r, \ 


t 
80 


90 


240 





10-12 


... 420 


290 


190 




47 


23 


750 


450 


12-14 


. . . 490 


330 


200 




47 


23 


540 


300 


14-16 


... 700 


390 


220 




47 


23 


400 


260 


16-18 


.. . 1,140 


525 


240 




47 


23 


300 


240 


18-20 


. . . 2,500 


660 


285 




47 


23 


280 


210 


20-22 


... ... 


760 


360 




47 


23 


240 


160 


22-24 





1,230 


450 




47 


23 


215 


140 


24-26 


... ... 


. . . 


560 




47 


23 


180 


125 


26-28 






780 




47 


23 


160 


115 


TABLE X— T 


HREE NO. 


2 D. B. R 


. C. CABLES 


IN 1% 


IN. BLACK- 




ENAMELED 


CONDUIT 




$ 




Temperature 
Range, deg. C. 


r 
90 


— Heating 
125 


Load, 


An 

180 


■n 




Cooling 

(Am] 
45 


Load 


ip. 


270 


j. ; 



10-12 


460 


150 




56 




19 


780 


390 


12-14 


575 


180 




56 




19 


560 


330 


14-16 


720 


180 




56 




19 


430 


300 


16-18 .... 


1,250 


180 




56 




19 


340 


270 


18-20 


2,400 


200 




56 




19 


260 


210 


20-22 


... 


270 




56 




19 


210 


180 


22-24 


•.... ... 


310 




56 




19 


190 


150 


24-26 


... 


410 




56 




19 


170 


120 


26-28 





520 




56 




19 


150 


100 


TABLE XI—: 


DHREE NO. 


1 D. B. E 


. C. CABLES IN iy 2 - 


IN. BLACK- 




ENAMELED 


CONDUIT 








Temperature 
Range, deg. C. 


r 
100 


— Heating 
125 


Loac 
150 


L, Ai 






Cooling 
(Amp 
50 


Load 


np. 
200 


300 


• ) 




10-12 


. . . 420 


225 


115 




68 


20 


810 


540 


12-14 


. . . 540 


240 


122 




68 


20 


600 


375 


14-16 


. . . 600 


250 


130 




68 


20 


450 


300 


16-18 


. . . 750 


275 


135 




68 


20 


405 


245 


18-20 


. . . 960 


300 


150 




68 


20 


315 


210 


20-22 


. . . 2,700 


375 


165 




68 


20 


285 


200 


22-24 


• • • • • • 


480 


190 




68 


20 


220 


160 


24-26 


• • ■ • • • 


580 


200 




68 


20 


195 


150 


26-28 .... 


• • • • . • 


730 


225 




68 


20 


180 


140 






DISTRIBUTION, TRANSFORMATION, SWITCHING 85 

Time in Seconds Required to Raise or Lower Temperature 

(Continued) 



TABLE XII— 


THREE NO 


. D. B. 


R. C. CABLES IN 2 


-IN. BLACK- 




ENAMELED 


CONDUIT 








Temperature 
Range, deg. C. 




-Heating '. 
175 


,/-\Q f\ A ■)->"» 1~| 




Cooling 
(Am] 
62% 


Load 


r 
125 


LiUcL-iXy fillip. 

250 


375 





10-12 


405 


125 


64 


23 


960 


480 


12-14 


495 


150 


64 


23 


630 


390 


14-16 


660 


160 


64 


23 


510 


320 


16-18 


960 


170 


64 


23 


420 


270 


18-20 


400 


180 


64 


23 


360 


225 


20-22 


2,400 


190 


64 


23 


315 


195 


22-24 


. . . . ... 


215 


64 


23 


280 


170 


24-26 


. . . . ... 


240 


64 


23 


240 


150 


26-28 




280 


64 


23 


210 


135 


TABLE XIII— T 


HREE NO. 


00 D. B. 


R. C. CABLES IN 


2-IN. BLACK - 




ENAMELED 


CONDUIT 








Temperature 
Range, deg. C. 


150 


-Heating ] 
225 


/-ion A -m t-v 




Cooling 
(Amj 

75 


Load 


jUdllj -fillip. 

300 


450 





10-12 


420 


146 


51 


22 


1,080 


525 


12-14 


480 


146 
146 


51 
51 


22 

22 


720 
600 


375 


14-16 


580 


325 


16-18 


740 


146 
146 


51 
51 


22 
22 


500 
420 


300 


18-20 


1,110 


270 


20-22 


. . . . 1,740 


1.46 


51 


22 


345 


240 


22-24 


2,400 


146 
146 
146 


51 
51 
51 


22 
22 
22 


285 
240 
200 


220 


24-26 




200 


26-28 




185 



TABLE XIV— THREE NO. 000 D. B. R. C. CABLES IN 2-IN. BLACK- 
ENAMELED CONDUIT 



Temperature 
Range, deg. C 

10-12 

12-14 

14-16 

16-18 

18-20 

20-22 

22-24 

24-26 

26-28 











Cooling 


Load 




—Heating Load, Amp — 




(Am] 


-v \ 


r 


> 


■M 


175 


262% 


350 


525 


87% 





620 


130 


63 


26 


1,275 


510 


735 


150 


63 


26 


840 


420 


900 


150 


63 


26 


540 


380 


1,140 


150 


63 


26 


440 


360 


1,560 


165 


63 


26 


405 


345 


3,600 


180 


63 


26 


380 


300 


. . . 


195 


63 


26 


360 


250 


. . . 


210 


63 


26 


325 


210 


... 


230 


63 


26 


280 


185 



86 ELECTRICAL AIDS TO GREATER PRODUCTION 



Time in Seconds Required to Raise or Lower Temperature 

(Continued) 

TABLE XV— THEEE NO. 0000 D. B. R. C. CABLES IN 2%-IN. BLACK- 
ENAMELED CONDUIT 



-Heating Load, Amp.- 



Temperature , 

Range, deg. C. 225 281 337 394 

10-12 270 120 100 71 

12-14 320 120 100 71 

14-16 330 135 100 71 

16-18 390 150 100 71 

18-20 420 165 100 71 

20-22 465 170 100 71 

22-24 600 180 100 71 

24-26 810 195 100 71 

26-28 ...... 1,260 210 100 71 



Cooling Load 

— , (Amp.) 

450 675 112y 2 

51 21 3,000 630 

51 21 1,800 540 

51 21 1,320 450 

51 21 990 420 

51 21 640 330 

51 21 480 280 

51 21 405 240 

51 21 330 210 

51 21 300 175 



TABLE XVI— THREE NO. 300,000-CIRC. MIL. D. B. R. C. CABLES 
IN 2% -IN. BLACK-ENAMELED CONDUIT i 

















Cooling 


Load 


Temperature 


r 


Heating Load, Amp 






(Am 


n 1 




> 


?•) 


Range, deg. C. 


275 


343 


410 


482 


550 


825 


137 





10-12 


.. 600 


250 


165 


120 


77 


31 




930 


12-14 


.. 670 


260 


180 


120 


77 


31 


2,400 


780 


14-16 .... 


.. 800 


280 


190 


120 


77 


31 


1,650 


690 


16-18 .... 


.. 870 


300 


195 


120 


77 


31 


1,170 


630 


18-20 


.. 960 


330 


225 


120 


77 


31 


900 


570 


20-22 


. . 1,200 


360 


240 


120 


77 


31 


720 


470 


22-24 


. . 1,800 


380 


255 


120 


77 


31 


600 


375 


24-26 


. . 2,000 


420 


270 


120 


77 


31 


550 


310 


26-28 




470 


285 


120 


77 


31 


465 


300 



TABLE XVII— THREE NO. 400,000-CIR. MIL. D. B. R. C. CABLES 
IN 3-IN. BLACK-ENAMELED CONDUIT i 

Cooling Load 

Temperature , Heating Load, Amp. * (Amp.) 

Range, deg. C. 325 406 487 568 650 975 162i/ 2 

10-12 600 250 165 120 77 31 ... 930 

12-14 670 260 180 120 77 31 2,400 780 

14-16 800 280 190 120 77 31 1,650 690 

16-18 870 300 195 120 77 31 1,170 630 

18-20 960 330 225 120 77 31 900 570 

20-22 1,200 360 240 120 77 31 720 470 

22-24 1,800 380 255 120 77 31 600 375 

24-26 2,000 420 270 120 77 31 550 310 

26-28 470 285 120 77 31 465 30C 

i Figures for this and next size of wire are based on the assumption that 
N. E. Code carrying capacity would produce the same temperature rise in 
these conductors as is found in the 500,000-circ. mil. cable. No tests were 
made on these two sizes. 



DISTRIBUTION, TRANSFORMATION, SWITCHING 87 

Tr\£E in Seconds Required to Raise or Lower Temperature 

(Continued) 

TABLE XVIII— THREE NO. 500,000-CLRC. MIL. D. B. R. C. CABLES 
IN 3-IN. BLACK-ENAMELED CONDUIT 

Cooling Load 

Temperature , Heating Load, Amp. ^ (Amp.) 

Range 400 500 600 700 800 1,200 200 

10-12 600 250 165 120 77 31 ... 930 

12-14 670 260 180 120 77 31 2,400 780 

14-16 800 280 190 120 77 31 1,650 690 

16-18 870 300 195 120 77 31 1,170 630 

18-20 960 330 225 120 77 31 900 570 

20-22 1,200 360 240 120 77 31 720 470 

22-24 1,800 380 255 120 77 31 600 375 

24-26 2,000 420 270 120 77 31 550 310 

26-28 470 285 120 77 31 465 300 

right is given the time in seconds required for the conductor to 
lose 2 deg. within the same ranges of temperature considered 
for the heating, and provided no current is flowing. 

The usefulness of these tables is based on the assumption that 
no attention need be paid to the heating of a conductor until it 
approaches the limits imposed by the operating conditions. If 
intermittent loads continue long enough, there will be a steady 
rise in the temperature of the conductor until a point is reached 
at which the cooling is rapid enough to prevent further heating. 
The higher the temperature attained the less increase there will 
be with a given current and the more rapid will be the dissipa- 
tion of heat during the "off" period. Again, taking the table 
for No. 14 wire as an illustration, it can be seen that 20 amp. 
will require 120 seconds to cause a rise of 2 deg. from 10 to 12, 
and that it will require 180 seconds to lose this heat. If the 
temperature is allowed to rise to 14 deg., however, it will require 
130 seconds for the rise from 12 to 14, and the loss of the two 
degrees will take place in 135 seconds. With 20 amp. " on " and 
"off" for equal lengths of time there will, therefore, be a con- 
tinuous rise in temperature until a trifle above 14 deg. has been 
reached. The same table also shows that if 45 amp. exists for 
12 seconds and it is not desired that the temperature rise should 
go above 16, an off period of 120 seconds would be required. In 
any case, whenever the " on " and ' ' off " times of the current are 
in the same ratio as the heating and cooling times given in any 
horizontal line, the ultimate temperature rise of the conductor 
will range between the limits given in the left-hand column in 



88 ELECTRICAL AIDS TO GREATER PRODUCTION 

the same line. If a current equal to that indicated at the top 
of the next to the last column is maintained the time required for 
a reduction of two degrees will be found below opposite the tem- 
perature range being considered. 

The use of the tables can best be explained by an example: 
A small electric welder requires a current of 50 amp., and the 
greatest length of time during which this current is in use is one 
second, while the shortest off time is two seconds. The present 
requirements of the National Electrical Code in this case are for 
a No. 6 conductor; but if the table for No. 10 wire is observed 
and the column headed "50 amp." traced, it will be seen that in 
50 seconds a temperature rise of 2 deg. will take place. Keep- 
ing in mind that the cooling time in this case may be twice as 
long, it can be seen from the column for zero load horizontally 
to the left of 100 seconds that a temperature of between 20 deg. 
and 22 deg. will exist. This is the temperature the conductor 
will attain if it is subject to the operating conditions given for a 
long time or indefinitely. If this temperature is considered too 
high for the conditions, the next table for No. 8 niay be consulted. 
In this are no heating and cooling times that balance so nicely, 
but in the 14-16 deg. line is a heating time of 165 seconds and 
a cooling time of 210. This signifies that the temperature of the 
conductor will remain below 16 deg., and since the heating period 
from 12 to 16 is 300 seconds and the cooling time between 12 
and 16 is 610, the temperature rise will be between 12 and 16 
deg. In any case it is evident that No. 6 wire is larger than 
necessary. 

On a chart representing a fluctuating load all short-time use 
of current appears is recorded in the form of triangles. Cur- 
rents of longer duration usually form approximations to square 
or oblong bodies, and their effective values may be easily calcu- 
lated. Now the root-mean-square value of a sufficient number 
of evenly spaced altitudinal lines in a triangle is about 58 per 
cent of the extreme altitude. The speed of the paper will affect 
the appearance of the triangle, but as long as the base is ex- 
pressed in seconds and the altitude in amperes this will not mat- 
ter. Hence in all those graphs which approximate a triangular 
form the root-mean square current may be estimated by striking 
off the top 42 per cent and widening the triangles at the place 
where they are cut off to the width of the base. It must be 
noted that in a calculation of this kind there is no need of any 



DISTRIBUTION, TRANSFORMATION, SWITCHING 89 

great degree of accuracy since no two duty cycles show the same 
result. On this account the period showing the heaviest use of 
current should be selected. 

By the use of the tables the proper size of wire to use 
with any intermittent load may be found in a simple manner. 
A casual inspection of Fig. 41 shows (neglecting the highest 
peak load) an average of about 750 amp. "on" and "off" for 
about equal lengths of time. It is essential to find out what this 
will bring about in two conductors of 500,000 circ.mil in parallel. 
For this purpose, as there are two wires in each leg, the current 
is divided by 2, which gives 375 amp. on one wire "on" and 




40 30 

Time in Seconds 



Fig. 41- 



-Method of Approximating Root— Mean— Square Value of 

Current 



"off" for equal lengths of time. Bearing in mind that heating 
and cooling periods should be about equal and that the current 
during the "off" period is about 200 amp., the approximate 
temperature rise may be found from Table XVIII. For 400 
amp. heating and cooling times are about equal between 18 deg. 
and 20 deg. C. But as the cooling time is shorter than the heat- 
ing time and the current 25 amp. less than that for which the 
heating time is given, some allowance may be made for this and 
the final temperature reached after many such cycles assumed 
to be about 15 deg. 

The influence of the peak should now be estimated. It is 
equivalent to 1400 amp. lasting about seven seconds with an 
"off" time of about fifty-five seconds as the chart shows. Half 
of 1400 is 700, and this current, as Table XVIII indicates, will 



90 ELECTRICAL AIDS TO GREATER PRODUCTION 

require 120 seconds to raise the temperature of the conductor 
2 deg. Considering the cooling period under 200 amp. (the 
nearest data available) as a criterion, it appears that the cooling 
time would be 1170 seconds. The ratio of 120 to 1170 seconds is 
about one to nine. This also points to a temperature rise of 
about 18 deg. However, since the 375 amp. half-time load pro- 
duces a higher temperature than a continuous 200-amp. load, 
the cooling will not be quite so rapid as the figures indicate and 
the final temperature would run somewhat higher. 

PREVAILING TREND IN GROUNDING PRACTICE 

The characteristics of different types of ground connections 
and the field to which each type is fitted for use were discussed 
by W. C. Wagner, electrical engineer of the Bureau of Standards, 
in a paper presented before a meeting of the Western Associa- 
tion of Electrical Inspectors. He pointed out that the driven- 
pipe ground connection is economical and reasonably satis- 
factory for lightning protection grounds and low-voltage cir- 
cuits when high-potential and low-potential conductors are not 
likely to cross and when the resistance is not required to be less 
than a few ohms. Driven pipes are easily inspected, readily 
removed and do not require large ground areas. 

The latter advantage is important in places where the ground 
must be installed in restricted space or under pavements. Mr. 
Wagner said: "A greater depth of penetration than 10 ft. (3 
m.) in conducting soil is not, in general, economically advisable. 
An earth connection to be efficient must be below the frost line, 
because a variation in resistivity of more than 200 per cent 
may be expected in reducing the temperature from 20 deg. C 
to — 20 deg. C. Several driven pipes connected in parallel de- 
crease the resistance of the ground connection when the pipes are 
separated from 1 ft. to 8 ft. (0.3 m. to 1.8 m.). A pipe ground 
should not be made near a pole because the pole exerts a shielding 
effect and shuts off a large part of the current flow. Mechanical 
considerations will usually govern the choice of size of driven 
pipe, but it has been found that the best results can be obtained 
with pipe from 0.75 in. (19.1 mm.) to 2 in. (5.08 cm.) in diam- 
eter." 

Buried plates are not used to any extent because the driven 



DISTRIBUTION, TRANSFORMATION, SWITCHING 91 

pipe grounds are more convenient and give the same results in 
most cases. The area of a single plate in ordinary conducting 
soil cannot be economically increased beyond 20 sq. ft. (1.8 sq. 
m.) and should not be buried deeper than 8 ft. (2.4 m.). It is 
usually better to bury two smaller plates some distance apart and 
connect them by a wire than to bury a larger plate of the same 
ground resistance. The surrounding soil greatly affects the use 
of buried plates, and an increase of conduction can be obtained 
by surrounding the electrode with salt or a bed of coke. Mois- 
ture changes do not affect a coke bed, because the coke bed'con- 
stitutes virtually an extension of the electrode. Coke has the 
disadvantage as compared with salt of requiring excavation, as 
the latter can be carried into the ground by moisture from a 
pocket at the surface. Coke also exerts a corrosive action where 
iron is used and is generally considered more detrimental than 
salt. Copper electrodes should be used where long life and mini- 
mum attention is desired. Strips should be used where bedrock 
is near the surface of the ground and it is impracticable to em- 
bed pipes or plates deep enough to provide an effective earth 
connection. This is especially true in soil of high resistivity 
because of the electrostatic capacity in the case of a strip is 
greatest for a given amount of metal. This method is also appli- 
cable, therefore, for use in high-resistance soil where driven pipes 
would be used. 

Water pipes give less resistance to ground than any other of 
the methods discussed. "A water pipe in an average soil," Mr. 
Wagner said, ' ' has approximately the resistance of from fifty to 
sixty driven pipes or buried plates in parallel. Pipe systems are 
easily accessible at the service entrance. Moreover, the areas 
covered by electric lighting systems are approximately the same 
as those covered by water mains. This method of grounding is 
therefore advantageous and in the case of low-voltage alternat- 
ing-current circuits does not appreciably affect the water-piping 
systems. ' ' 

Method of Making Secondary Grounds. On the Memphis 
(Tenn.) Gas & Electric Company's secondaries, grounds are not 
made to water systems and the practice of grounding at frequent 
poles is not used. Instead one ground is placed on each second- 
ary, not more than 200 ft. (61 m.) from the transformer and at 
the side or back of a house near the service entrance, said C. K. 



92 ELECTRICAL AIDS TO GREATER PRODUCTION 

Chapin. superintendent of distribution, before another meeting of 
the Western Association of Electrical Inspectors. The ground is 
made by placing a 12-in. (30.2-cm.) square of sheet zinc 7 ft. 
2.1 m.) or 8 ft. (2 A m.) below the surface of the earth and 
connecting it to the secondary with Xo. 6 B. £ S. gage weather- 
proof wire inclosed in a 0.75-in. (19-cm.) pipe. The pipe ex- 
tends about 9 ft. (2.7m) above the surface of the earth, thus 
putting the ground wire out of reach of curious persons. The 
zinc-plate ground used in Memphis will discharge the entire sys- 
tem satisfactorily, and in doing so the maximum voltage between 
secondary system and the earth reaches 500 volts at a distance 
of 300 ft. (92 m.) from the ground plate. The ground plate is 
compelled to dissipate only from 400 watts to 700 watts, thus a 
very small current has to pass through the ground wire. 

The grounds are tested when installed for maximum resistance 
of 20 ohms at 1 amp. Many tests show that a secondary ground 
when crossed with the primary will increase its internal resistance 
three or four times. When two such crosses do not occur on dif- 
ferent phases at the same time, the system will continue to dis- 
charge through the ground without surging such as would prob- 
ably occur in the case of ground to water mains. A ground 
properly installed will probably last from ten to fifteen years, but 
rigid inspection and maintenance are necessary on all grounds. 
Failure of the zinc-plate ground can only occur when the trouble 
is not located and removed promptly. The time to bake out a 
good ground depends greatly upon the weather conditions, but 
usually is two to five hours, which gives adequate time for the 
location and removal of trouble. 

DUCT SPLICING SAVES SHORT LENGTHS OF CABLE 

The financial loss due to inability to utilize short lengths of 
cable is a serious one to all companies operating underground 
systems of distribution. These lengths are constantly accumu- 
lating owing to withdrawal of old cable necessitated by changes 
and replacements of existing circuits. In view of these facts the 
experience of one of the large lighting companies in the develop- 
ment and use of duct splices as related by J. B. Xoe and A. 
Rabe of the New York Edison Company will be cited. 

How Splice Diameter Is Minimized. The underground de- 



DISTRIBUTION, TRANSFORMATION, SWITCHING 93 

partment of this company made such a splice in November, 1904, 
joining two sections of three-conductor, 250,000-circ. mil., 6600- 
volt cable. The diameter of the splice was kept down by stag- 
gering the joints in the three conductors, making a joint 24 in. 
(71 cm.) long, over which was placed a split lead sleeve slightty 
larger than the original cable, soldered at the seam and wiped to 
the cable sheath at the ends. This joint was made by drawing 
in the first section, making the splice in the manhole, and then 
resuming the pulling, drawing the splice and second section on 
into the duct. This original duct splice remained in service 
without failure for several years and when finally withdrawn for 
some cable changes was opened and found perfect. 

In 1911 the proposed addition to the system of about twenty- 
five high-tension service connections offered a tempting opportu- 
nity for the extensive use of duct splices. More than six miles 
(9.7 km.) of feeder were made, using old cable exclusively. Not 
one failure has ever occurred in any of these splices or on any 
of the more than 600 duct splices made on various cables. 

In 1915, the accumulation of short lengths again becoming criti- 
cal, serious attention was turned to the duct splice. Before 
adopting it as a permanent policy for all types of cable, tests 
were conducted to determine : 

First — Mechanical strength, both of the spliced sleeve and the 
spliced conductor, as compared with the strain put on them in 
installing and withdrawing the cable under the severest duct 
conditions. 

Second — Dielectric strength of the duct splice after it had been 
subjected to the strain of installation. 

Third — Heating in the duct splice due to heavy loads. 

All of these tests showed the duct splice as made up to be 
superior to the body of the cable. 

A decided improvement was made at this time by "burning" 
on the lead sleeve instead of using solder. This made the joint 
as flexible as the rest of the cable, and as the spliced lengths 
could be put upon reels without fear of cracking, it became the 
practice to make the joints in the cable yard instead of in the 
manhole, effecting a very great saving in cost. At odd times and 
on rainy days the short pieces were spliced up to make sections 
of such lengths as could be easily matched. 

Among the various types of cable on which the duct splice has 



94 ELECTRICAL AIDS TO GREATER PRODUCTION 

been used, two deserving of special mention are triplex 350,000- 
circ. mil, 25, 000- volt armored submarine cable and single-con- 
ductor 2,500,000-circ. mil low-tension cable with pressure wires. 
During 1916 a duct splice was developed for two-conductor, 
1,000,000-circ. mil low-tension concentric cable with three pres- 
sure wires. 

Some idea of the amount of cable transformed from scrap or 
very slow-moving stock to actual service may be gained from the 
fact that the company has to date a total of 211,569 ft. (approxi- 
mately 64,460 m.) of duct-spliced cable of various types, repre- 
senting a value of approximately $380,000. Practically all of 
this material is now installed. 

ADVANTAGES OF WOOD DUCT FOR UNDERGROUND 

SYSTEMS 

Although the dielectric qualities of wood duct are not so good 
as those of fiber duct, extensive testing by R. A. Paine, Jr., gen- 
eral foreman of details and records, Edison Electric Illuminating 
Company of Brooklyn, has shown that they are sufficient for 
the requirements of low-voltage 115-230 volt distribution mains 
and services. Low installation and maintenance costs are ob- 
tained by the use of wood duct. The cost per unit length is only 
slightly greater than that of fiber and tile, and it requires no 
concrete envelope. 

In the following tabulations of tests, creosoted wood duct, 
which is used by telephone companies, was adopted. Its inside 
diameter is SVs in. (7.9 cm.), and it is 4^2 in. (11.4 cm.) square 
on the outside. 

Breakdown Tests. An alternating-current breakdown voltage 
test was made on four pieces of wood duct and four pieces of 
fiber duct in order to show the comparative insulating value of 
wood and fiber duct. Pieces No. 1 were sealed at one end, filled 
with water and allowed to stand forty-eight hours. Pieces No. 2 
were sealed at one end, placed in a barrel of water, keeping the 
inside duct dry, and allowed to stand forty-eight hours. Pieces 
Xo. 3 were placed in a barrel of water, allowing inside and out- 
side of duct to be in contact with water for forty-eight hours. 
Pieces Xo. 4 were taken from stock. 

Three test sections were taken from each piece, using tinfoil 



DISTBIBUTION, TRANSFORMATION, SWITCHING 95 

electrodes and increasing the voltage by steps of 500 volts after 
each minute, and the following average breakdown values were 
obtained : 



Fiber duct 
Wood duct 



Piece No. 1 


Piece No. 2 


Piece No. 3 


Piece No. 4 


9,300 


8,700 


4,300 


i 


1,000 


1,000 


800 


2,200 



Resistance to Short Circuit. The resistance of wood duct to 
arcs as compared with fiber was determined by the following 
tests : To determine what the results would be if a short circuit 
occurred on distributing mains in the duct, three legs of 150,000- 
circ.mil R. & L. cable were placed in fiber duct and punctured 
so that they would short-circuit. A slow-burning short resulted, 
when they were connected to the source of energy, which burned 
three holes in the bottom of the duct, the fiber bursting into 
flame. This flame would probably have consumed the whole 
piece of duct, but it burned so fiercely that it had to be extin- 
guished. 

For the same experiments with wood three lengths of the duct 
that had been soaked in water for five days and two stock lengths 
were tested. Three legs of 150,000-circ.mil R. & L. cable were 
placed in the ducts and punctured so that they would short- 
circuit. A very high temperature was generated in the ducts 
when they were connected to the mains, and this was allowed to 
increase until the cables burned in half and cleared themselves. 
This operation was repeated four times, twice over the joint and 
twice in the middle of the length on both the water-soaked and 
the dry duct. From the water-soaked duct a relatively small 
amount of thick black smoke or gas was generated at each short. 
This smoke or gas did not seem to be combustible, and the duct 
was in very nearly perfect condition after the test. A very 
large amount of greenish white smoke was liberated at each short 
in the dry duct. One short burned for five minutes, destroyed 
two cables and filled up the bottom of the duct with molten cop- 
per and lead. After this short the duct smoldered near the joint, 
liberating a large amount of smoke. 

It was shown that the wooden duct was better than fiber in 
case of a short circuit occurring in the conduit, because the latter 
may easily be entirely destroyed. The durability of wooden duct 

i Piece No. 4 of the fiber duct withstood 11,500 volts for five minutes. 



96 ELECTRICAL AIDS TO GREATER PRODUCTION 

is apparent from the extensive use and experience which tele- 
phone companies have had with it. 



THE ECONOMICAL LOADING OF TRANSFORMER 

BANKS 

Where several transformer banks of similar characteristics are 
available to carry a variable load it is of interest to determine 
the economical point for switching an additional unit into serv- 
ice. Ordinarily this is done when the load has reached the ca- 




1500 1000 2500 3000 3500 4000 
Load in Kilowatts 
Fig. 42 — Losses in Three-phase, 3000-kva. Transformers Under 

Variable Loads 

Gives comparison between losses in one unit carrying total load and two 
units each carrying one-half of total. 

pacity of the working units, but this may not always be the most 
economical practice. Obviously, switching in an idle unit will 
increase the total core losses which are constant for each unit, 
but the corresponding decrease in the variable or copper losses 



DISTRIBUTION, TRANSFORMATION, SWITCHING 97 

may more than counterbalance this increase. As the ratio be- 
tween these losses differs widely in different classes of trans- 
formers, it is necessary to investigate each case individually. 

Fig. 42 is a sample set of curves indicating the losses in a 
3000-kva. three-phase transformer for varying loads and power 
factors. From this the loss in kilowatts may be read directly 
for any load at any power factor. The curves are plotted in 
kilowatt load rather than kilovolt-amperes, as the load may be 
read directly in kilowatts on the station meters and will thus 
permit the operator to pick the economical switching point more 
readily than if expressed in kilovolt-amperes. The curves are 
based on test results or data furnished by the transformer manu- 
facturer. On the same sheet is plotted a second set of curves 
showing the total losses in two transformers, each carrying half 
the load. These curves may be calculated from the first set. 

For instance, at unity power factor and 1500-kw. load, the 
loss in one transformer is seen to be 24.5 kw. Therefore, for a 
total load of 3000 kw., if two transformers are used the total loss 
will be 49 kw., which gives one point on the unity power-factor 
curve of the second set. Each loss curve for two units intersects 
the corresponding loss curve of one unit, beyond which point of 
intersection it will be more economical to operate two units than 
one. It will be noted that in the particular example given the 
economical point on the unity power-factor curve is at 3430 kw. 
(or kva.), or slightly more than full load. On the 70 per cent 
curve the intersection is at 2440 kw., or 3486 kva. Thus it will 
be seen that the economical point of change is at a practically 
constant kva. load regardless of power factor. It will also be 
noted that the economical switching point is at a constant value 
of loss regardless of power factor, and that this point is that at 
which the total loss in one transformer is three times the core 
loss in one transformer. 

Similarly, with the two units in service it will be most eco- 
nomical to switch in a third when the core loss per transformer 
equals one-sixth the total copper losses or when the core loss in 
one of the pair equals two-thirds the copper loss in one of the 
pair. In a general way, when n units are running switch to 
n -f- 1 units, when the losses per transformer are W e = nW cn / 
(n + 1). 

These results are plotted in Pig. 43 for a number of eombina- 



98 ELECTRICAL AIDS TO GREATER PRODUCTION 

tions. Knowing the load per unit, the operator can tell at once 
when it will be economical to switch a unit on or off. If the load 
is known in kva., the division points on the unity power-factor 
line should be used. 

"While the above equation holds true only for groups of iden- 




zooo 



3500 



Z500 3000 

load in Kw. per Unit 

Fig. 43 — Economical Switching Loads 
Thus if the load reaches 3000 kw. at 87 per cent power factor, it becomes 
economical to switch in a second transformer. 



tical transformers or other apparatus having losses partly con- 
stant and partly varying with the square of the load, the graphi- 
cal investigation may be suitably modified to apply to generators, 
dissimilar transformers or other apparatus. 



TRANSFORMER CONNECTIONS FOR EMERGENCY 
MOTOR STARTING 

Where transformers arranged for three-wire secondaries are 
connected in delta for service to three-phase motors the neutral 
points may be connected to one side of a double-throw switch to 
provide half voltage for starting. This scheme is one which has 
been much used in the past and should never be overlooked in 
emergency cases. 



DISTRIBUTION, TRANSFORMATION, SWITCHING 99 

A modification of this system may be readily applied where 
transformers having 2300/460- volt secondaries are in use to fur- 
nish low voltage for starting 2300-volt motors. In such trans- 
formers only two secondary leads are available, and it is neces- 
sary to run an extra lead out of the case. If connections are 
made as shown in the upper part of the accompanying illustra- 
tion, 53 per cent of full voltage can be procured for starting. 
This will ordinarily afford good starting torque without an ex- 
cessive rush of current. 



No. I 



'RANSORMER SECONDARIES 

No. 2 

J? 



No. 3 




RUNNING SIDE 



TO MOTOR 



O 



STARTING SIDE 



^rti 



1 



EXTRA LEAD BROUGHT 
THROUGH SPECIAL 
BUSHING IN CASE 



?3 P.D. T. OIL SWITCH WITH 
-i LOW VOLTAGE AND 
OVERLOAD RELEASE 





Fig. 44 — Connections for Obtaining Different Starting Voltages 

with Vector Relations 



This connection was recently used successfully in operating a 
350-hp. motor from three 100-kva. transformers after the auto- 
starter had burned out. The double-throw oil switch was 
equipped with low-voltage and overload release. If this voltage 
is insufficient, 60 per cent or 72 per cent normal voltage may be 
obtained by tapping, as shown by the vector diagrams at the 
bottom of the illustration. 



100 ELECTRICAL AIDS TO GREATER PRODUCTION 

FROM TWO- TO THREE-PHASE WITH STANDARD 

TRANSFORMERS 

Where two-phase service is supplied and three-phase energy is 
desired, but only standard transformers are available, the follow- 
ing plan can be followed: Assume that the primary voltage is 
2200 and that 2200/220-110-volt transformers are available. 
Connecting the primary windings of two transformers across the 
two phases and joining the secondary of one transformer with 
the mid-point of the other transformer's secondary will not give 



Wvww 

/VW\ AVA 



A- 



YVVWWWN 
< ■ ■ 

M/W| AWA 



UwWWW 



Fig. 45 — Method of Connecting Three Standard Transformers to 
Convert from Two-phase to Three-phase 



balanced three-phase voltages, since the secondary windings do 
not have the proper number of turns, relatively, for T-operation. 
In fact, operating the transformers mentioned above in T the 
phase voltages x would be 228, 261 and 261. 

By connecting a third transformer across phase A to "buck" 
the primary voltage of transformer 3 by 220 volts, however, the 
voltages across phases are made nearly equal, as shown by the 

i Based on actual measurements for a specific installation — voltages 
across windings 1 and 2 were both 114, while voltage across winding 3 was 
235. 



DISTRIBUTION, TRANSFORMATION, SWITCHING 101 

following calculations: Voltages across both windings 1 and 2 
were 110 volts and the pressure across winding 3 was 198 volts. 
Thus the voltage across windings 1 and 2 would be 220 volts, 
while both the other delta voltages would be 



V HO 2 + 198 2 = 227 volts. 
This scheme was proposed by E. Charles Seares. 



TRANSFORMER RECORD CARD 

Reproduced below is a transformer record card that has been 
used for several years with success by a Western company. The 
two sides of the card are shown, one side giving a complete rec- 



^v 



TRANSFORMER RECORD 



G. E. 



H, Form G 



MAKER'S No. COMPANY'S No. 

A3 7/4/6 2563 



prim IIOOO IOSOO • IOOOO 



.ILL. 



ZSOO - 4GO 



*50 r d £d f'7-IS 



I INSTALLED | REMOVED 



STATION No 



7/4$ 



SO 1 1 



6/700 



5 I IS 



II 2 IS 



2 Z 16 



,°*r •" 



IQ,1 15 



I 3 16 



Primary Bushing Broken 



A- 



y~ 



TEST RECORD 



4 '9 15 



IQ-IO-IS 



.'•8-16 



2+8 



245 



245 



.043 



-040 



.Q4-I 



22 OOP 



22000 



22 OOP 



OK 



OK 



OK_ 



Repaired Primary Bushing 



OIL RECORD 



OATE CHANGED 



IQ • 10 ■ IS 



I -8-16 



Flushed Coifs 



Fig. 46 — Form of Transformer Record and Test Sheet Used by 

Western Company 



ord of the life of the transformer and the other side test infor- 
mation and condition of oil. It will be noted that the form 
records exclusively information with reference to the trans- 



102 ELECTRICAL AIDS TO GREATER PRODUCTION 

former. Information concerning the load connected to a trans- 
former after it is installed is put on a second card file, which 
contains transformer station numbers, arranged numerically, 
whereas in the transformer card file the transformers are ar- 
ranged numerically by location number. A cross reference be- 
tween these two files is in the one case the transformer number 
and in the second case the location number. Location numbers 
are arranged in such a way that the number tells at a glance the 
district and feeder to which the transformer is connected. The 
location number appears on the cover and side of each trans- 
former in white letters 2 x /2 in. (6.4 cm.) high, easily legible and 
not likely to be obliterated. 

SCHEME FOR INSPECTING TRANSFORMER 
INTERIORS 

Often it becomes necessary to inspect the windings or interior 
connections of oil-immersed transformers. To overcome the dif- 
ficulties of using a lamp and trying to see through the oil, one 
Southern central-station company is employing a telescoping tube 
the lower end of which is sealed with a glass disk to prevent oil 
filling the tube and obstructing vision. A lamp is attached to 
the outside of the tube near the lower end so that the glare of 
the filament will not reach the user 's eye. When the proper volt- 
age is not available for operating an incandescent lamp, a flash- 
lamp may be attached to the tube. The tube is made of five sec- 
tions, each about 2 ft. (61 cm.) long. This device enables the 
men to inspect the interiors of oil-immersed transformers without 
getting into the oil as is sometimes necessary. 

CARRYING OVERLOADS BY INCREASING PRIMARY 

VOLTAGE 

It is often possible to carry increased load without adding 
copper to the distribution system by raising the primary voltage, 
provided, of course, that the secondary voltage is held at its nor- 
mal value. Too great an increase in primary voltage, however, 
would seriously increase iron losses of transformers on the lines. 
Voltages may usually be raised economically as much as 10 per 
cent. Curves of iron loss and exciting current as affected by the 



DISTRIBUTION, TRANSFORMATION, SWITCHING 103 

impressed voltage are shown in the accompanying illustration, 
from which it is seen that the power losses in transformers in- 
crease very rapidly with primary voltage. 

230 

+■ 
J3 260 

O240 

| 220 

«>200 

c 160 

© 

$ 160 
o 

^140 

2 

- 120 
£ 

5 ioo 
o 

0. 



eo 



40 











































c 












































































































































































































,/ 


/ 
/ 


D 


































^y 


" . 




* 


L. 






























*^c< 


»» * 


p *** 


. 


-< 


•— 


B 
A 
























j^g 


•■^^ 


5^- 


**- • 






















rs~. 


£? 


*^ 


^ 


























zs 


"ZZ 



















































































90 I Z 



1 9 110 



3. 4 95 7 6 9 100 I . 2 3 4 105 6 
Per Cent, rated Voltage 

Fig. 47 — Variation of Iron Loss and Exciting Current with Voltage 
Curves B and C show iron loss and exciting current respectively for large 
units. Curves A and D give corresponding values for small units. Curve 
E gives iron-loss variation from a number of tests. 

This suggestion, as well as the curves reproduced here, were 
contributed by W. B. Stelzner. 



REDUCING THE COST OF INDUSTRIAL SWITCH- 
BOARDS 

A new development in switchboards for industrial plants, con- 
ceived by Louis F. Leurey of San Francisco, is being adopted by 
many concerns doing industrial plant wiring on the Pacific Coast. 
By eliminating the use of copper busbars and marble panels and 
substituting instead insulated wire leads properly housed and 
iron pipe or angle-iron framework carrying inclosed switches, 
these companies are building boards at low cost. It is reported, 
moreover, that the boards thus built are operating just as satis- 
factorily as any of the older types. If it is desired to make the 
job appear more complete, steel-boxed panels made of ordinary 
sheet steel can be used, but these boards are still inexpensive. 



104 ELECTRICAL AIDS TO GREATER PRODUCTION 

Eliminating the necessity for busbars effects a still further reduc- 
tion in cost. The mains are brought to the switchboard in con- 
duit or can be run either across the front or the back of the 
board in galvanized-steel troughs made by any tinsmith. This 
box has flanged sides to which a removable cover is screwed. 
Taps to each switch are made through ordinary types of con- 
nectors. This construction is said to be not only less expensive 
in first cost but also to permit extensions and changes at costs less 
than those incident to changes on boards with which bar copper 
is employed. 

One particular advantage of these boards is that they may be 
made up on short notice because all of the necessary material can 
easily be secured locally and very little machine work is neces- 
sary. On marble and slate panels made to specifications in the 
factory delaj^s are likely to occur. Another advantage is that 
these boards need to be made to conform only to the require- 
ments of space available and equipment to be mounted. Panel- 
boards, on the other hand, must be laid out according to certain 
prescribed standard panel dimensions. This advantage of flex- 
ibility is considered especially important where electrical appa- 
ratus is to be installed in a structure already built. It is ex- 
pected that these boards will grow in favor as the necessity of 
conserving copper and eliminating unnecessary transportation of 
such heavy products as slate becomes more urgent. 

Actual Installation Cost of Inexpensive Switchboard. Cost 
data have been compiled to show the inexpensiveness of one type. 
They measure 18-in. (45.7 cm.) by 84 in. (203 cm.), and the 
average group consists of two or three panels. On the panels are 
mounted three triple-pole, single-throw, fused, 100-amp., 500-volt 
switches manufactured by the Square D Company, Detroit, Mich. 

Each switch controls an average of 50 hp. in motors, and the 
total cost of erection with labor at $7 per day was $140 per 
panel. Therefore the average cost per horsepower of motors 
controlled would be $140 divided by 150 hp., or 90 cents. This 
cost includes the panel-board completely erected with all pipe 
connections made and wire installed. It does not include, how- 
ever, the necessary sheet steel, condulets and angle iron used in 
the panel. These items are not estimated because they vary con- 
siderably in the different parts of the county and they repre- 
sent only a minor part of the total expense. 



DISTRIBUTION, TRANSFORMATION, SWITCHING 105 

REBUILDING A FEEDER BOARD WITHOUT STOPPING 

SERVICE 

Reconstruction of a three-wire feeder board to provide for 
double the number of circuits formerly handled was undertaken 
by the Pacific Gas & Electric Company in an interesting manner 
at Station C. Since the circuits controlled could not be de- 
energized for the entire period required for reconstruction, the 
work was done without interrupting service at all, this being 
accomplished by the use of a temporary panel. 

The original board consisted of twenty-one 3-ft. by 7%-ft. 
(91.4-cni. by 228-cm.) marble panels, each one consisting of two 
sections — 28 in. (73 cm.) and 62 in. (157 cm.) high respectively. 
All of the switches (two double-throw single-pole knife switches 
to each positive and negative circuit) and the ammeters (one for 
the positive and one for the negative circuit) were on the upper 
or larger panel, the lower one being blank and serving only to 
give a finished appearance to the board. The positive meters 
were along the top of the board and the negative meters just 
below. As two sets of negative and positive busbars arranged 
in one horizontal plane were in use, and all of the switches were 
in one horizontal row, considerable copper had to be used for 
jumpers between the busbars and switch lugs. 

To provide for the new circuit it was decided to install the new 
switches on the lower blank panel and regroup the meters on the 
upper panels to allow for those required for the new circuits. 
The latter operation was accomplished without disfiguring the 
panels by inverting the upper panel, plugging the old holes with 
plaster of paris and drilling new holes as required. The am- 
meters covered most of the plugged holes. To avoid the use of 
excessive amounts of copper, all of the switches on the upper 
panel were used as positive switches and those on the lower panel 
as negative switches. This required a rearrangement of the bus- 
bars. Instead of using four busbars in one horizontal plane as 
before, one busbar was supported back of each row of switch lugs, 
thus requiring only short jumpers and making the back of the 
board more accessible. This arrangement utilized the entire 
space of the panels giving four feeders to a 3-ft. (91.4-cm.) 
panel, which before accommodated only two circuits. Further- 
more, a more orderly arrangement of switches was secured. 



106 ELECTEICAL AIDS TO GREATER PRODUCTION 

To accomplish, reconstruction without cutting out a single 
feeder, a temporary two-feeder panel was installed and the two 
feeders from the first panel of the board were connected with it 
by jumpers. This arrangement cleared one complete panel so 
that it could be taken down, redrilled and put back in place 
according to the rearranged plan. Since the capacity of each 
panel was doubled by the arrangement, the temporary panel was 
required only while the first unit was being rebuilt. Thereafter 
the additional capacity gained by the revised connections took 
care of each additional unit as it in turn was reconstructed. 

The necessity of making the change without interfering with 
the service made the work consume much more time than would 
have been ordinarily required. However, the complete recon- 
struction of the connections was effected in about ten months by 
one journeyman and a helper. The satisfaction attendant upon 
the use of the rearranged board is such that the company has 
adopted this panel arrangement as standard. 

SELECTION OF FUSES FOR INDUCTION MOTORS 

Although fuses are quite commonly employed in motor-circuits 
their use is liable to be attended with uncertain results when 
starting and operating induction motors, the starting current of 
which may greatly exceed the full-load current, unless they are 
properly applied. The accompanying table brings out a few of 
the difficulties which may be experienced in the attempt to select 
a fuse with a rating adapted both to starting conditions and to 
ordinary running conditions. 



STARTING CURRENT OF THREE-PHASE, 60-CYCLE SQUIRREL-CAGE 

INDUCTION MOTORS 

/ — Starting with Light Load — » r— Starting with Full Load — N 



Manu- 


Per Cent of 




Per Cent of 




facturer's 


Full-Load 


Time 


Full-Load 


Time 


Indication 


Current 


Involved 


Current 


Involved, See 


1 


600 


Instantaneous 


600 


5 


2 


500 to 600 


Instantaneous 


500 to 600 


5 to 8 


3 


600 


Instantaneous 


600 


6 


4 


450 to 500 


Instantaneous 


450 to 500 


4 to 5 


5 


600 


One-half second 


600 


30 


6 


500 to 600 


Instantaneous 


500 to 600 


5 


7 


600 


Instantaneous 


600 


6 


8 


500 


Instantaneous 


500 to 606 


6 to 8 



DISTRIBUTION, TRANSFORMATION, SWITCHING 107 

From this table it is apparent that in many cases of starting 
induction motors a fuse selected to protect from overload is very 
likely to blow at starting and a fuse capable of carrying the 
starting current will not protect for ordinary conditions of opera- 
tion. Hence in those cases where the motor is started and oper- 
ated through the same fuses it is necessary to take into account 
the starting current, the time interval over which the high start- 
ing current flows and the time lag of the fuse itself. Such tests 
show that these factors vary over quite wide limits for different 
fuse types and to some extent for the same fuse at different 
periods. 



CONVENIENT ARRANGEMENT OF FUSES ON 
FEEDER PANELS 

Considerable waste of space and an unsightly installation have 
usually been found to result from the design of feeder panels in 
which bus connections and fuses are a part. On several occasions 
H. Burt Foote has found it necessary to design feeder panels for 
three-phase, 440-volt and 500-volt alternating-current circuits. 
As a result of some thought and consideration of the require- 
ments the construction shown herewith has been worked out. 

Switches with 600-volt spacing in ratings of 30 amp. and 60 
amp. combined with 600-volt fuses usually make an awkward 
arrangement. So the 100-amp. size with 250-volt spacing, as 
this is also permissible for 600 volts alternating current and 
adaptable to circuits up to 50 hp. Selection of this type gave 
uniformity and besides, this switch possesses enough mechanical 
strength to adapt it to general use, which is not true of the 30- 
amp. and 60-amp. size with 600-volt spacing. Placing fuses on 
the front of a panel increases its size, making additional expense 
and a waste of space. As ordinarily placed on the back of a 
panel, they cover a portion of the studs and bus connections, mak- 
ing it difficult to tighten up a loose joint and inconvenient to get 
access to the outgoing feeders. These difficulties have been over- 
come, and the fuses are so placed that they bear a direct relation 
to the switches and that the connection from switch to fuse is 
reduced to a minimum. 

The distribution boxes on which the fuses are mounted are 



108 ELECTRICAL AIDS TO GREATER PRODUCTION 

made of sheet metal fastened as shown to the panel supports and 
forming a side inclosure for the back of the panel. The conduit 
enters them in a neat manner at top or bottom, and the wires are 
led direct to the fuse blocks through a bushed hole. Where 
more than one panel is used the adjacent boxes may be combined 



jnTTCia c^mmz^ 



kl fr 



JUL 



JUT 



Jd 



w 



w~ 



f # w 

B U S E S 



w w 



4 



<FUSES 



(A) 



*LL 



^OUTGOING 
..-CIRCUITS 



r — I 



a 



o 



m i 


> ®\ 






i® i 


^ o| 


Q\ 








i<°> « 


) 




®\ 











(B) 

Fig. 48 — Arrangement of Fuses and Distribution Boxes 

in one. The front-connection fuse blocks make them interchange- 
able for any size of circuit. The busbar construction will be 
found to be very simple and accessible. 



PREVENTING INSTALLATION OF WRONG-SIZED FUSES 

Safety stickers of the style shown herewith may be pasted on 
fuse cabinets to serve a twofold purpose. They are a precaution 
against the use of wrong-sized fuses, and they emphasize the fact 
that it is dangerous to let the body become the connecting link 



DISTRIBUTION, TRANSFORMATION, SWITCHING 109 



between live wires and a good ground. When the fuse sticker is 
pasted in the cabinet box and an inspector later discovers the 
wrong fuse in use he has tangible evidence that previous warn- 



FOR SAFETY 



USE ONLY 
lO AMP. FUSES 

OKLA INSPECTION BUREAU 



CAUTION! 

DO NOT STAND IN DAMP PLACE 
OR TOUCH ANY GROUNDED 
METAL OR CONDUIT WHILE 
TOUCHING METAL SOCKETS OR 
LIVE WIRES. 

KEEPCABINET BOX CLOSED 

OKLAHOMA INSPECTION BUREAU 



Fig 49 — Samples of Stickers Pasted on Fuse Cabinet Boxes to Give 
Evidence of Previous Inspection 

ing had been given and can act accordingly. H. J. Clark of the 
Oklahoma Inspection Bureau reports that the stickers are very 
effective. 

PANEL FOR TESTING DIFFERENT-SIZE FUSES 

Shown in the illustration on page 110 is an easily made 
panel which may be used in industrial plants for testing various 
types of fuses. As will be noted, both sides of the fuse blocks 
are connected in multiple. One side is connected directly to the 
supply line, while the other side is connected to the line through 
a 10-watt lamp. The placing of a good fuse in any fuse block 
will light the lamp. 



SPECIAL USES FOR POTHEADS 

Two interesting and economical uses of disconnecting potheads 
have been worked out by N. L. Allen, electrical engineer for the 
American Zinc Company of Tennessee. Sometimes, in connec- 



110 ELECTRICAL AIDS TO GREATER PRODUCTION 

tion with the operation of its concentrator, it is necessary to re- 
verse certain motors when the belts are thrown off for repairs. 
Since it is not necessary to do this very often, three G. & W. 
disconnecting potheads have been installed at each motor in the 
three-phase leads to permit reversing the leads quickly and to 
avoid the necessity of reversing controllers. Of course, where 
the reversing of motors is more frequently necessary reversing 
controllers are provided. Another use of potheads is in the leads 




TO SUPPLY CIRCUIT 



PLUG TYPE 

30-AMP. CARTRIDGE TYPE 
60-AMP. CARTRIDGE TYPE 
500Y0LT CARTRIDGE TYPE 
CLIP TYPE 

Fig. 50 — Fuse-testixg Paxel for Differext Sizes 

from the surface feeder to the feeder bus in the mine. The 
feeders on the surface, which operate at 2300 volts, three-phase, 
60 cycles, are connected by means of disconnecting potheads at 
the pole to steel-armored, lead-covered, paper-insulated cable con- 
taining three No. 4 copper wires. These cables go down into 
the mine a distance of about 500 ft. (152.4 m.) to the feeder bus. 
A spare cable is provided for emergencies. Both of these cables 
are "phased out" and marked so that the potheads at both ends 
can be quickly and properly changed in case of damage to the 
operating cable. 



WALL ENTRANCE FOR USE WITH FLAT BUSBARS 

To prevent birds and cold air entering its transformer room in 
the winter and yet give proper ventilation and insulation for 
outgoing busbars the arrangement shown in Fig. 51 was used by 
a large cotton mill in New England. Two 10-in. (25.4-cm.) by 



DISTRIBUTION, TRANSFORMATION, SWITCHING 111 

0.25-in. (0.64-cm.) bars'per leg are used in the secondary circuit 
where it runs through the wall, the spacing between phases being 
6 3/16 in. (15.7 cm.). Ebony asbestos wood is used around each 




Fig. 51 — Details of Bus Entrance to Transformer Room 

pair of bars with slate between the asbestos wood and the build- 
ing walls. To secure the spacing mentioned asbestos slabs are 
inserted as shown. The pressure on the buses is 6600 volts. 



TWO METHODS OF BENDING CONDUIT 

Elaborate apparatus does not have to be employed for bending 
conduit if an outfit like the one illustrated herewith is con- 
structed. The principal part of the outfit consists of two 6-in. 
by 6-in. (15.2-cm. by 15.2-cm.) timbers 12 ft. (3.6 m.) long with 
a 314-ft. (1.14-m.) timber of similar size bolted across the end as 



^m 



Detail A 



Cut and Adjust 
for Curvature 
as Desired. 



Bolted 



4ConqjJit^Z§— 




Fig. 52 — Details of Conduit Bender 



shown. This end of the frame is laid on a sawhorse or pile of 
bricks or stone, one end of the conduit to be bent being placed 
beneath the cross timber, and another cross timber, modified as 
shown in detail A, placed across the frame beneath the portion 
of the conduit which is to be bent. Downward pressure may 



112 ELECTRICAL AIDS TO GREATER PRODUCTION 

then be applied to the free end of the conduit, causing it to bend 
over the unfixed cross timber. 

Another simple but effective method has been developed by 
E. A. Phipps of the Rockingham County Light & Power Com- 
pany, Portsmouth, N. H., that has saved considerable time and 
labor in the reconstruction of this company's power plant. The 
outfit consists of a frame upon which a jack can be placed to 
press against a shoe conforming to the general shape of the con- 
duit. Other shoes are provided at the upper corners of the 
frame, where they are pivoted so that they will adjust them- 
selves to the curvature of the conduit. The effectiveness of the 
equipment depends chiefly upon the drawing effect of the shoes. 

The outfit will bend any iron-conduit pipe from 1.25 in. to 4 in. 
(3.2 cm. to 10 cm.) or larger in diameter, using any make of jack 
on the market. The device is light, portable, easily operated by 
one man, and can be used in straightening as well as in bending 
conduit. It will make a 90-deg. bend without flattening the pipe 
considerably because the recess in the shoe immediately over the 
jack is relatively deep. Only one piece — the central block — has 
to be changed in adapting the bender to different-size pipe. The 
frame occupies a space of only about 3 ft. (0.9 m.) high by 3 ft. 
(0.9 m.) long by 18 in. (45 cm.) wide. A bender of this type has 
been used at Portsmouth, where more than 20,000 ft. (6096 m.) 
of conduit, requiring every variety of bend, was necessary, with- 
out destroying a single piece of stock. Furthermore, a great sav- 
ing was effected by not using the usual heating method. It is 
estimated that the machine easily paid for itself in making the 
first fifty bends. 

TAPPING A 13,200-VOLT THREE-CONDUCTOR CABLE 

When it is necessary to make branch and Y joints on three- 
conductor, 13,200-volt cables the method described below, which 
has been found satisfactory by E. B. Meyer, assistant to chief 
engineer Public Service Electric Company, Newark, N. J., may 
be used. 

The ordinary specifications for making a straight joint are fol- 
lowed, except that a 6-in. by 28-in. (15.2-cm. by 71.1-cm.) Sleeve 
is used instead of a 4-in. by 20-in. (10-cm. by 50.8-cm.) sleeve. 
A copper connector of a sufficient size to accommodate two con- 



DISTRIBUTION, TRANSFORMATION, SWITCHING 113 

ductors laid side by side is employed. The ends of the through 
cable are cleaned in the same manner as usual. After the end 
of the tap is cleaned in a similar way it is bent slightly and laid 
parallel to one of the through cables, which have been butted to- 
gether. A connector somewhat larger than the conductors is 
spread over them and all are sweated together. Then each leg is 
insulated in the usual manner, and in addition the tape is 
threaded through the Y-shaped branch formed by the tap and 
conductors. In belling the end of the lead sleeve at the doable 
end it will be found necessary to cut away a portion of the> lead 
to conform to the shape of the two cables leading into the splice. 
A small piece of sheet lead may be required to form a backing 
for the lead between the cables. Filling of the joint is done in 
the usual manner. 



CHAPTER III 

MOTORS, CONTROL, SPECIFIC APPLICA- 
TIONS, TROUBLES AND REMEDIES 

INDUSTRIAL APPLICATIONS OF ELECTRIC POWER 

There can be no doubt as to the vast influence which manufac- 
tured power has had in the industrial development of the county 
during the last few years. In fact, it is problematical whether 
this remarkable progress in manufacture would have been real- 
ized without the corresponding development in ways and means 
of applying power which have characterized many steps of indus- 
trial efficiency. 

These applications of power have been greatly affected by the 
electric motor because of its high efficiency in both large and 
small sizes, and moreover by the increased flexibility in transmis- 
sion and distribution permitted with electricity as a substitute 
for the older methods of line shafting and belt drives. 

The peculiar character of the work calls for the specially 
trained engineer who has ability to analyze not only the electrical 
problems connected with the motor and its operation, but who 
can, moreover, analyze with equal skill the mechanical features 
of the machinery to be driven and thus combine in his solution 
the most efficient types of motor and control to operate the ma- 
chinery at lowest first cost and the least possible operating 
expense. 

That this is particularly difficult engineering is evidenced by 
the fact that more than ordinary trouble has been experienced 
in finding men capable of handling successfully the problems con- 
cerned with motor applications, including, as such problems do, a 
large proportion of mechanical as well as electrical engineering 
details, and often presenting perplexing and indefinite features. 
In other words, the special province of the application engineer 
is to take a given problem with many factors and indefinite rela- 
tions and reduce them to a definite basis by careful study and 
analysis. 

114 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 115 

One of the most striking points is the fundamental importance 
of the motor in the conservation of labor expense, a feature set 
forth clearly by contrasting the great differences between various 
typical industries on the basis of the value added to the product 
by manufacture. 

In the study of factory power, and more particularly of the 
electric motor, the outstanding items of power economy and in- 
creased production may be looked upon sometimes as dependent 
merely on the relative electrical and mechanical efficiencies of 
the various motors, on the one hand, and the actual increase in 
output brought about through a motor-driven machine, on the 
other. While these two items do constitute the starting point in 
most of the problems, the expert is confronted with a large num- 
ber of factors, any one or all of which may make up the net 
advantages included by these two primary items. 

Any given example may thus be resolved into a study of the 
type of motor and control available for the particular require- 
ments, corresponding study into the mechanical requirements 
themselves, and a summary of the operating conditions which 
may be expected to follow application of the motor. These con- 
siderations are rendered more valuable by proper emphasis upon 
the economies afforded by the adoption of such a system of drive 
in comparison with older methods. 

FOR AND AGAINST SYNCHRONOUS MOTORS 

The synchronous motor has always been supposed to have cer- 
tain drawbacks which limited its application for industrial drive. 
First among them was low starting torque. Second, since a syn- 
chronous motor runs at a fixed speed (the direct-current field 
of the rotor is locked to the alternating-current field of the stator) 
no slip is allowed ; therefore the flywheel effect was supposed to 
be limited. Complication due to the separate exciter has also 
been cited. A fourth objection is sometimes made, viz., that syn- 
chronous motors require more careful attention and more skilled 
operators than other kinds. In order to determine the advisabil- 
ity of installing synchronous motors these four objections must 
be considered in turn and the question answered in view of the 
facts. This is the purpose of this article by Will Brown. 

The Starting Torque. It is necessary to make a distinction 



116 ELECTRICAL AIDS TO GREATER PRODUCTION 

between a synchronous motor's operation during the starting 
period up to the point of pull-in and its operation after syn- 
chronism, has been attained. The critical point in starting a syn- 
chronous motor is the pull-in. Like a squirrel-cage motor, it 
starts and increases speed up to a certain point, known as its 
rated slip speed. This slip-speed rating varies according to the 
load. At this point of maximum speed as an induction motor a 
synchronizing torque must be exerted to pull the rotor field up 
into step with the rotating field of the stator. This operation 
may be compared to paralleling an alternator on the line. All 
operators have observed the large synchronizing power which is 
exerted as the incoming alternator approaches the frequency of 
the line. It is the same thing with the synchronous motor. The 
line current might be considered as gripping the field of the rotor 
and yanking it up into step. 

It can be readily understood that the more slip there is in the 
rotor speed at the pull-in point the greater must be the torque 
exerted to pull the rotor up to full speed. It is possible to 
increase the initial starting torque by increasing the resistance in 
the damper bar windings, but this results in a larger slip or 
lower speed at the pull-in point. Therefore the limit of load 
which can be ''pulled in"' at a specified kva. input determines the 
starting torque. The future will doubtless see a considerable 
improvement in this pull-in characteristic of synchronous motors. 
By proper design it may be possible to change the pull-in peak 
current so that the same work can be done by lower current in- 
put over a longer space of time. Synchronous motors can now 
be designed to start and pull into step a load amounting to from 
30 to 50 per cent of full load with a kva, input not to exceed 250 
per cent of normal rating. It is probable that the time will come 
when the synchronous motor can be made to start and pull in its 
full rated load with a kva. input which will not exceed safe oper- 
ating limits. 

Use of Clutches. AYhen the starting duty is so severe that a 
synchronous motor cannot handle it — on heavy line shafts, for 
instance — the solution may be found by the proper use of 
clutches. There are two types of clutches used, viz.. mechanical 
and magnetic. The cost of a magnetic clutch is higher, but it 
has a number of points of superiority for certain types of duty. 
such as automatic safety control, etc. The variation of the grip 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 117 

on the clutch faces allowed by magnetic control can often be 
used to good advantage. 

Among certain industrial plant operators of the old school 
there has been a widespread prejudice against the use of clutches. 
Their favorite remark was: "Oh, I wouldn't bother with a 
clutch. I get a slip-ring motor big enough to start the load and 
that 's all I care about. ' ' 

It is true that they could do this very thing in the past, but 
it is equally true that they are not going to be able to continue 
doing so. Central stations supplying power to these kinds of 
motors on this kind of drive have learned a lesson. They are 
going to demand high power factor, and the use of large syn- 
chronous motors for driving line shafts is one solution. Proper 
clutch installations will take care of severe starting duty. 

The Northern States Power Company, at Minneapolis, has a 
number of flour-mill loads, many of them driven by slip-ring 
motors. There have also been quite a few installations of syn- 
chronous motors belted or directly coupled to the line shafts. 
According to their experience, the synchronous motors are su- 
perior to the induction motor for this service. They have 
proved more satisfactory to the power used in point of efficiency 
and to the power company in point of power factor. The above 
company has recently ruled that it will allow nothing but syn- 
chronous motors on loads of this kind about 100 hp. 

The clutch problem, after all, is not the bugbear that many 
operators think it is. Trouble in the past has often been due to 
the fact that too small a clutch was installed. It was not always 
the buyer's fault either. Many clutches were overrated by the 
manufacturers. The buyer would select a clutch too small and 
then his troubles would begin — clutch linings would burn out 
and necessitate shut-downs. The result was that the plant 
owner would condemn all clutches. With the selection of a 
clutch of proper size to allow sufficient margin for all condi- 
tions of starting and running there should be no trouble. Most 
assuredly it will pay engineers to investigate this subject of 
clutches from an impartial standpoint. At the present time 
clutch manufacturers are very willing to make the necessary en- 
gineering investigations and recommend the proper size amply 
to take care of the load. 

Those who have studied the present performance of syn- 



118 ELECTRICAL AIDS TO GREATER PRODUCTION 

chronous motors must admit that while low starting torque has 
been one of the chief objections in the past, motors as now de- 
signed are able to carry a wide variety of loads without trouble. 
A still greater improvement in starting characteristics is likely 
to further widen the application of such motors for industrial 
drive. 

The subject of flywheel effect required for synchronous motor 
drive is too technical to discuss in an article of this kind. Syn- 
chronous motors as now designed with normal excitation can 
stand instantaneous overloads of several hundred per cent. In 
fact, the pull-out point of a synchronous motor can be made so 
high that it is far beyond the heating limits of the machine. It 
is true that the synchronous motor does not allow the flywheel 
to act over a definite slip period as does the induction motor. 
There is, however, a certain amount of "give" between the 
direct current field and the alternating-current field on the syn- 
chronous motor as the load increases instantaneously. That is, 
the motor can slide back a portion of a pole face, and during this 
brief interval the flywheel is allowed to act. This helps consid- 
erably in taking care of the sudden jolts of the load such as 
those at the end of the stroke on compressors and o'ther recipro- 
cating machines. 

On certain heavy, fluctuating loads it is possible to use a 
magnetic clutch with the magnetic pull on the clutch lining set' 
to allow slippage at a certain maximum load. When the load 
exceeds this there will be a slip between the two halves of clutch, 
and the flywheel can carry part of the load. An interesting 
example of such an installation may be seen at the Trap Rock 
plant, Dresser Junction, Wis. A single line shaft is driven by 
a 600-hp., 200-r.p.m. synchronous motor. From this line shaft 
several crushers and other machinery are driven by ropes or 
belts. There is one large jaw crusher capable of receiving a 
full carload of rock in the hopper. Two large flywheels, ap- 
proximately 16 ft. (4.8 m.) in diameter, weighing from 15 tons 
to 20 tons each, are set on each side of the crusher. When the 
heavy peak comes on the crusher the magnetic clutch slips, al- 
lowing the flywheels to help carry the load. 

The third objection, previously mentioned, namely, the com- 
plications due to a separate exciter, is not a very serious one 
and is much more than offset by the advantage that S3 T nchronous 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 119 

motors can supply the necessary magnetizing kva. for induction 
motors to counteract the lagging power factor they produce. 
Very little trouble or inconvenience arises from the separate 
excitation since it involves no more complication than there is in 
the exciter circuit of any direct-current machine. 

Unity-Power-Factor Operation. Motors which are to drive 
mechanical loads at the highest efficiency should be operated as 
nearly as possible at unity power factor. Motors operated in 
this manner constitute a non-inductive load, and while they do 
not operate at leading power factor, except at infrequent inter- 
vals, they do help improve the power factor of a line to a limited 
extent. 

The design and construction of synchronous motors for unity- 
power-factor operations differs from synchronous condensers 
in the following respects : 

First — The field winding need not carry so large a current 
for unity-power-factor operations, therefore field copper is some- 
what reduced. Also the rating of the exciter is reduced to about 
half the size of exciter used for a condenser. Since the field 
current is thus limited, it is impossible for the motor to operate 
at a low leading power factor anywhere near its kva. rating at 
unity power factor. At very low leading power factor such a 
motor could carry less than one half its normal kva. 

When a motor is operating at leading power factor the field is 
overmagnetized from an exterior source of magnetization, in 
this case the direct-current exciter. When the motor is running 
at lagging power factor the field is magnetized from the alter- 
nating-current side. Since this magnetizing current is in quad- 
rature with the voltage, it has zero power factor and produces 
no heating effect in the field. This explains why the field heat- 
ing in a synchronous motor is high at leading power factor and 
low at lagging power factor. 

Second — Among the differences between a synchronous motor 
designed for unity-power-factor operation and one designed for 
power-factor correction is that no rheostat is necessary for con- 
trolling the field of the synchronous motor of the first type. 
This eliminates rheostat losses and helps efficiency to a slight 
extent. 

Third — It has often been said that a synchronous motor is 
merely an alternator supplied with damper windings on the pole 



120 ELECTRICAL AIDS TO GREATER PRODUCTION 

faces. This is not quite correct. In any alternator the shape 
of the pole tip as well as the extent of the pole span is limited 
by the field leakage which the poles must withstand when ope- 
rating at low lagging power factor. Since it is not necessary to 
provide for such a condition with a synchronous motor operating 
at unity or slightly leading power factor, it is possible to design 
the pole faces and pole tips so as to get much better distribution 
of the slots for the squirrel-cage winding, and thus succeed in 
reducing the actual electrical air gap. (This is different from 
the mechanical air gap.) This makes it possible to reduce the 
amount of excitation necessary to produce a certain specified 
pull-out torque. It can be seen that such a design of pole con- 
struction will reduce the field losses and increase the efficiency 
of the unit as compared with the alternator (shorter pole span) 
type of design. Manufacturers who use the same design for 
their synchronous motor poles that they use for the alternator 
poles cannot take full advantage of the above-mentioned oppor- 
tunities. 

A synchronous motor designed to operate at full-load unity 
power factor will be from 10 to 25 per cent lower in price than 
a synchronous motor designed to operate at low leading power 
factors. This comparison is based on prices including exciter in 
both cases. 

Attention Required. The fourth objection, that synchronous 
motors required more careful attention and more skilled ope- 
rators than induction motors, is less important to-day than it 
was a few years ago. Most operators who are capable of han- 
dling induction motors of larger sizes can easily learn to start 
and operate synchronous machines. In the past the manual 
operation of starting a synchronous motor was often done in 
rather a crude and unscientific manner. Starting has now been 
simplified to such an extent that any careful operator can start 
a synchronous motor without mistake. It seems quite likely 
that automatic starting devices will ultimately be installed for 
synchronous motors which will guarantee at all times the most 
efficient starting, regardless of the skill of the operator. 

After the motor is running at synchronous speed there is very 
little likelihood of " hunting" any more. Whenever such action 
arises it is generally due to faulty engineering in the installa- 
tion. Commutator trouble in the exciter is not nearly so likely 









MOTORS, CONTROL, SPECIFIC APPLICATIONS 121 

to arise with a synchronous motor operating at unity power factor 
as would be the case with an alternator where the power factor of 
the line is varying. Besides, exciters, as now designed, give 
comparatively very little trouble. 

After facing all the practical objections which can be made 
to synchronous motors we must admit that the advantages more 
than offset the handicaps — on heavy loads of constant speed. 
With ordinary intelligent handling they operate satisfactorily 
with very low maintenance cost. 

WHAT SYNCHRONOUS MOTORS CAN AND CANNOT DO 

In many discussions of synchronous motors the subject of 
power-factor correction and condenser capacity is mixed up 
with and allowed to overshadow the characteristics of motor 
performance. A motor should be judged, however, by its abil- 
ity to perform a certain duty and should stand or fall upon this 
performance alone. If it is able to improve the power factor of 
the system, this characteristic may then be considered as an ad- 
ditional point in its favor. 

Service That Synchronous Motors Cannot Give. Will Brown 
of the Electric Machinery Company points out that while syn- 
chronous motors as now designed are quite different from the 
modified alternators of older days, and can develop 30 to 50 per 
cent full-load torque at starting, there are certain duties they 
cannot perform. So as to clear up any misunderstandings that 
may exist concerning synchronous motors in regard to either 
their limitations or advantages, some of the purposes to which 
they cannot be adapted will be outlined first. 

(1) They cannot be used profitably on small loads. This 
generally means anything under 100 hp. An exception should 
be made in the case of small synchronous motor-generator sets, 
however. 

(2) They cannot be used on intermittent loads involving fre- 
quent starting and stopping, such as crane motors, reversible 
hoist motors, etc. 

(3) They cannot be used where variable speed or adjustable 
speed is demanded unless some mechanical means of regulating 
the speed change is provided. 

(4) They cannot be used where it is necessary to start up the 



122 ELECTRICAL AIDS TO GREATER PRODUCTION 

full load from rest unless a clutch or some other mechanical 
method of easing the starting condition is supplied. ' 

Uses to Which Synchronous Motors Are Adapted. In an- 
swer to the question which now probably arises in the reader 's 
mind, "Where are synchronous motors now in use?" Fig. 53 
is presented. It does not by any means cover the full field of 



1 

< 

> 


rYPES OF PLANTS USING 
SYNCHRONOUS MOTORS 

AND 

THE "MACHINES WHICH 


! 


i 

j 


I 

g 
§ 


1 


I 


5Q 

5 


1 


55 
ge 

| 


i 


i 






50 

1 

1 


I 

I 




s 

i 


1 


AUTOMOBILE PLANTS 






















BRICK AND CLAY PLANTS 




















DRAINAGE PLANTS 






















ELECTRIC LIGHT AND POWER PLANTS 






















FLOUR MILLS 


























FOUNDRIES 


























ICE AND REFRIGERATING PLANTS 
























IRON WORKS 




















IRRIGATION PROJECTS BU 


















MINES " tV S3 
















MARBLE AND STONE CUTTING PLANTS 




















METAL WORKING PLANTS 
















■ 


OIL REFINING PLANTS 




















PAPER MILLS 






















QUARRIES 1 1 




■ 
















R\IBBER MILLS 


















RAILROAD SHOPS i *"' 






















SHIPYARDS 


























STEEL PLANTS 


























SUCTION DREDGES 


























SEWAGE DISPOSAL PLANTS 






















■ 


STONE CRUSHING PLANTS 






















TEXTILE MILLS 
























WATER WORKS 


















MISCELLANEOUS E2BH 









Fig. 53 — Applications to Which Synchkonous Motors Are Adapted 



possible applications, but it does indicate the already wide range 
of these motors and the promise of a much greater use in the 
future. 

Where a heavy and fairly continuous load can be driven at a 
constant speed, there is generally an opportunity to install a 
synchronous motor. High efficiency and reliability of service 
are the two great essentials in such work. It is safe to say that 
a synchronous motor is always higher in efficiency than an in- 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 123 

duction motor of corresponding rating. At low speeds the ad- 
vantage in favor of the synchronous motor is even greater than 
at high speeds. 

There are many heavy.-duty machines which must be run at 
low speeds. Formerly, if these machines were to be driven by 
motors it was necessary to install some form of belt or gear 
drive. They can now be directly connected to synchronous mo- 
tors and operate efficiently at speeds as low as 72 r.p.m. 

Starting Ability. — The old handicap of synchronous motors 
was their inability to start up from rest while carrying a v me- 
chanical load. This handicap has been overcome to a greater 
extent than most engineers realize. There are practical exam- 
ples of large synchronous motors developing a starting torque 
as high as 50 per cent of full-load torque obtained without a 
prohibitively large kva. input. The future will probably bring 
even more remarkable results. 

It is a fundamental fact that a low-speed synchronous motor 
cannot develop as high an initial starting torque with the same 
starting voltage as the high-speed motor, it being understood 
that horsepower ratings of the two motors are the same. For 
example, a certain motor with a synchronous speed of 200 r.p.m. 
can develop a starting torque of 35 per cent of full-load torque 
on the 40 per cent voltage tap with an input of 130 per cent of 
full-load kva., whereas a 600-r.p.m. motor can develop a starting 
torque of 40 per cent of full-load torque on the 40 per cent volt- 
age tap with an input of 115 per cent of full-load kva. 

Variable Loads. — Many types of heavy-duty machines requir- 
ing variable output are now designed so that they can be started 
and driven by synchronous motors. For instance, in a certain 
reciprocating pump installation a variable stroke is automatically 
obtained by means of bell cranks and by shifting the cylinder. 
This permits varying the delivery from zero up to 4200 gal. 
(15,900 1.) per minute. 

Mechanical methods for changing the inlet or outlet passages 
for fans and blowers permit the use of constant-speed motors 
where formerly only adjustable-speed motors could be used. 
There are already a number of such installations — for instance, 
large exhaust fans such as are used on mine shafts, etc. — and 
it seems quite likely there will be many more in the future. 

Line-Shaft Drive. — In cases where manufacturing processes 



124 ELECTRICAL AIDS TO GREATER PRODUCTION 

are so correlated that a line-shaft drive is preferable to indi- 
vidual motor drive, the synchronous motor is finding wide ap- 
plications. The motors may be either direct-coupled or belted. 
For this service it is nearly always necessary to use a clutch, 
either mechanical or magnetic, to permit starting and bringing 
the motor up to speed before the load is thrown on. The writer 
knows of a number of installations of this type in flour mills, 
also in rubber mills, all of them operating very satisfactorily and 
handling heavy loads, in which there are at times considerable 
fluctuations. 

Efficiency and Ruggedness. — The high efficiency which can be 
secured with a synchronous motor is well illustrated in the fol- 
lowing installations : One marble-working concern has been 
operating a 150-hp. synchronous motor driving a line shaft for 
nearly four years. The choice originally lay between an induc- 
tion motor and a synchronous motor. The higher efficiency ob- 
tained by the synchronous motor brought a saving in the first 
two years of operation which more than made up for the higher 
original cost of the synchronous motor. 

There is a rather interesting installation in a paper mill where 
a 1 150-hp. synchronous motor is driving two direct-coupled pulp 
grinders. No difficulty has been experienced either in starting 
or running. An induction motor of similar horsepower driving 
a similar load has caused more or less trouble, which is generally 
traced to the very small air gap. The slightest wear in the 
bearings alters the air gap sufficiently so that a very heavy 
magnetic pull is set up on one side of the rotor and quickly 
wears the bearings down still more until the time arrives when 
the motor must be stopped and the bearing repaired. Very fre- 
quently the windings of the armature are damaged also. The 
synchronous motor, owing to its comparatively large air gap, is 
much more rugged and dependable for operation on low-speed, 
direct-connected loads. 

Air-Compressor Drive. — Air compressors, especially those of 
sufficiently large capacity to require 100 brake horsepower or 
more, can be economically and efficiently driven by a synchro- 
nous motor. The old idea that it was necessary to change the 
piston speed with change in air demand has been abandoned. 
Mechanical methods of regulation on the compressors now per- 
mit the driving motor to operate at a uniform speed. 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 125 

In practice synchronous motors are used both belted and direct 
connected to the compressor. On direct-connected units the 
speeds required are generally within the range of 260 r.p.m. 
down to 120 r.p.m. Probably the greatest number of direct- 
connected synchronous-motor-driven compressors operate at a 
speed in the neighborhood of 200 r.p.m. This speed is very 
much higher than was ever thought advisable by compressor 
builders a few years ago. The increased speed has been made 
possible by the adoption of a light plate valve with a low lift. 
The time required to open and close such a valve is so small that 
it permits operating the piston at much higher speeds. 

In starting an air compressor the pressure can be relieved by a 
by-pass so that the motor has only the friction load and inertia 
to overcome in breaking the compressor from rest. This is very 
easily taken care of without drawing excessive kva. from the 
line, and the motor can pull into synchronism without causing 
objectionable fluctuation of the line voltage. 

Since the load factor of a compressor is generally high, and 
since the power factor of a synchronous motor can be maintained 
at unity, a favorable rate can usually be secured when energy is 
purchased from a central station. The fact that these motors 
operate at unity power factor or lightly leading (at part loads) 
should appeal with even greater force to plants generating their 
own energy. The power factor and efficiency obtained with a 
typical direct-connected synchronous-motor-driven air com- 
pressor are shown in Table XIX. 

TABLE XIX— EFFICIENCY AND POWER-FACTOR TESTS OF 560-HP., 

225-R.P.M. SYNCHRONOUS MOTOR DIRECT-CONNECTED 

TO AIR COMPRESSOR 

Exciting current remaining constant at all loads 



Quarter 
Load 



Half 
Load 



Three- 

Quarters 
Load 



Full 
Load 



One-and-a- 

Quarter 

Load 



Efficiency . . . 
Power factor 



92.6 
per cent 



96 



96 



95.4 



95.6 
per cent per cent per cent per cent 



98 



100 



98 



16 \)6 y» iuu y» 

per cent per cent per cent per cent per cent 
Leading Leading Leading Lagging 



Recently there has been an enormous demand for large syn- 
chronous-motor-driven air compressors among the shipyards of 



126 ELECTRICAL AIDS TO GREATER PRODUCTION 

the country. They range in size from 150 hp. to 1200 hp. 
Among other lines of industries using synchronous-motor-driven 
air compressors might be mentioned mines, foundries, automobile 
factories, structural steel works; in fact, any industry where a 
large quantity of compressed air is used. In driving tunnels the 
air pressure can be maintained in the headings by means of a 
battery of low-pressure compressors driven by synchronous 
motors. 

Ammonia-Compressor Drive. — The large ammonia compressors 
used in ice plants (50-ton or over) are driven in exactly the same 
way as air compressors, by either belted or direct-connected syn- 
chronous motors. The starting duty required is somewhat more 
severe than in the case of air compressors, however. In order to 
obtain the required starting torque it is sometimes necessary to 
use a higher voltage tap on the starting compensator than would 
be necessary with the corresponding air-compressor installation. 
The large flywheel combined with the inertia and friction of 
other moving parts requires that the motor be specially designed 
to produce maximum starting torque. 

The preference for direct-connected synchronous-motor-driven 
ammonia compressors is very markedly shown in the ice and re- 
frigerating plants recently constructed or now in course of con- 
struction. It may be said safely that the energy cost with direct- 
connected synchronous-motor-driven machines is less per ton of 
ice manufactured than is the case with any other type of motor 
drive. 

Once it was considered essential, in order to meet the varying 
demands for ice, that the speed of the ammonia compressors 
should be adjustable. This is no longer necessary. In place of 
one large unit running at variable speeds, ice plants can have 
two or more smaller units which run at constant speed. By 
running different combinations of the compressors in parallel, 
fluctuation in demand can be easily cared for without any pro- 
vision for speed adjustment. When the demand drops to a 
minimum the smallest compressor only may be used, so the 
losses may be kept at the minimum It can be seen that the over- 
all efficiency of such a plant will be very much higher than in 
the old-fashioned variable-speed plant. 

Another method of varying the output of the compressor at 
constant speed is by means of an adjustable clearance pocket, or 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 127 



cylinder, at each end of the compression cylinder. By means of 
these the clearance can be increased and the capacity lowered 
to any desired point between full load and one-quarter load or 
even lower. Thus the flexibility of the compressor is fully equal 
to that of the old adjustable-speed compressors driven by low- 
speed Corliss engines. 

The efficiency curve of the synchronous motors is quite flat 
throughout a wide range of load, so that there is very little loss 
in efficiency on the part of the motor when run at part loads. 
As far as the compressor is concerned, the efficiency at part joads 
seems to be practically as good as at full load. This is due to 
the general conditions under which ice-manufacturing plants 
operate. The efficiency and power factor for a typical syn- 
chronous-motor direct-connected to an ammonia compressor are 
indicated in Table XX. 

TABLE XX— EFFICIENCY AND POWER-FACTOR TESTS OF 450-HP., 

200-R.P.M. SYNCHRONOUS MOTOR DIRECT-CONNECTED TO 

AMMONIA COMPRESSOR 

Exciting current remaining constant at all loads 



Quarter 
Load 



Half 
Load 



Three- 
Quarters 
Load 



Full 
Load 



One-and-a- 

Quarter 

Load 



Efficiency . . . 
Power factor 



87.7 
per cent 

70 
per cent 
Leading 



92.6 93.7 94 93.8 

per cent per cent per cent per cent 

94 99 100 99 

per cent per cent per cent per cent 

Leading Leading Lagging 



Direct-Connected Centrifugal Pumps. — Quite a number of 
installations of synchronous-motor-driven centrifugal pumps 
have been made recently. In most cases the motor is directly 
coupled (through flexible coupling) to the pump shaft. Start- 
ing requirements of a centrifugal pump can be met by a prop- 
erly designed synchronous motor. Before starting, the pump is 
primed. The discharge valve is closed when the motor starts, 
so the impeller merely churns the water. The load increases 
rapidly, running up to 30 per cent, or even 50 per cent, of full 
load as the motor approaches synchronous speed. When full 
voltage is applied and the motor is pulled into step, there is a 
momentary rush of current, which, however, should not be exces- 
sive and should fall almost immediately as the motor settles down 



128 ELECTRICAL AIDS TO GREATER PRODUCTION 

to synchronous operation. The maximum peak at pull-in should 
rarely exceed 150 per cent of the full-load kva. 

As long as the discharge valve is closed the impeller is churn- 
ing the water, and this energy is transformed into heat. If this 
operation is continued too long, steam might be generated. A 
small by-pass for liberating air relieves any possibility of steam 
pressure. Of course the proper thing to do is to open the dis- 
charge valve as soon as the motor is running at synchronous 
speed and allow the pump to begin discharging at its normal 
head. 

There are numerous cases where centrifugal pumps driven by 
synchronous motors are used for suction dredging. As the pipe 
lines which carry the discharge are extended from point to point 
as the dredge continues its work, a large change in the friction 
head occurs which necessitates two-speed drive for the pump. 
This requirement can be met by using a two-speed helical gear. 1 

Each installation of centrifugal pumps is a special problem, 
and both motor and pump must be designed as such if best 
results are to be secured. Generally speaking, centrifugal 
pumps are designed, to operate at constant speed. Synchronous 
motors with speeds as low as 72 r.p.m. are used directly coupled 
to low-head pumps. High-head pumps with speeds as high as 
1200 r.p.m., or even 1800 r.p.m., are also directly coupled. 

Unity Power Factor Operation. — A synchronous motor de- 
signed for so-called unity power factor operation has a fixed 
exciting current which cannot be exceeded, so that absolutely 
unity power factor cannot be maintained if the load fluctuates. 
As the load drops off the power factor will change to leading, but 
the change in power factor from full load to quarter load is sur- 
prisingly small. From one-and-a-quarter load to one-half load 
the change in power factor is less than 10 per cent. At one-half 
load the power factor is slightly leading and at one-and-a-quarter 
load slightly lagging. If the load should be removed entirely 
from the motor, it would operate at approximately zero power 
factor up to about one-half of its rated kva. capacity. (The fric- 

i In one plant using this drive which the writer inspected the energy 
cost was only five-sixths of the amount that fuel cost when steam was used 
for the same purpose. Furthermore, the motor-driven suction dredge was 
handling considerably more material. If the present price of coal was 
taken into consideration, the energy cost would be only about five-twelfths 
of the full expense. 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 129 

tion losses in the motor would constitute a load, so that in prac- 
tice the power factor could never reach zero.) The limitation 
to the exciting current prevents the motor from carrying its full 
kva. rating. Of course, variations of design will change the 
characteristics of motors, so the preceding statements are only 
general and must be modified under certain conditions. The 
extent to which a power user can afford to go in installing syn- 
chronous machines depends largely on the annual cost of power. 
The advantage to be gained may run anywhere from 10 per cent 
to 30 per cent of this amount. 

Correcting Power Factor. — In the case of an isolated plant 
generating its own alternating current, the use of an over-excited 
synchronous motor at a leading power factor is often very desir- 
able. Such a motor if properly designed may operate at a power 
factor, say, 80 per cent leading, while at the same time carrying 
three-quarters of its rated mechanical load in horsepower. 
Under this condition the motor may exert nearly the maximum 
corrective effect on the system's power factor. The magnitude 
of the system load and the power factor must be taken into con- 
sideration, however. 

This problem of power-factor improvement cannot be met in 
the future, as it has been in the past, simply by the central sta- 
tion installing large synchronous condensers. It will become 
more and more desirable to have a connected load of many fair- 
sized synchronous motors scattered over the sj^stem. This is 
much better from the standpoint of voltage regulation, trans- 
mission efficiency, etc., than the old method of combining all the 
power-factor correction for the circuit in one or more synchro- 
nous condensers. 

The result will be that central stations will encourage the use 
of sj^nchronous motors more and more on their lines. This tend- 
ency is already apparent in many sections of the country, espe- 
cially where large individual users of power are scattered over 
the system. 

INTERPOLE MILL MOTORS VERSUS NON-INTERPOLE 

By far the larger proportion of direct-current motors in steel 
mills require rapid braking, either by "plugging" — that is, re- 
versing at full speed — or by dynamic braking, says W. R. 



130 ELECTRICAL AIDS TO GREATER PRODUCTION 

Runner of the Westinghouse Electric & Manufacturing Com- 
pany. The former operation is the more severe of the two, as it 
will be seen that if a series or heavily compounded motor is re- 
versed when running at high speed the armature emf. adds to 
the line emf. The effect of this is cumulative, the increasing 
current causing an increasing armature voltage, the maximum 
value of the latter depending on the speed and the saturation of 
the magnetic circuits of the motor. While the peaks are of very 
short duration, the armature emf. sometimes goes to nearly 
double normal value and the current to three or more times the 
full-load value. As these peaks tend to produce flashing at the 
brushes, tests have been made to determine the effectiveness of 
the interpole in eliminating the flashing. That the interpole 
motor is better adapted to this service than the older type of 
motor was very clearly shown by the results obtained. 

The motors tested were all of the totally inclosed mill type, 
series-wound, and represent standard designs of interpole and 
non-interpole machines. That the motors of a given rating were 
very similar in speed, voltage and weight is shown in the follow- 
ing table. Likewise, their performance curves are very similar 
so that the comparison is made on an equitable basis : 

One-Hour Speed 
Rating, Hp. R.p.m. Voltage Weight, Lb. 

Interpole 80 480 230 4,550 

Non-interpole 75 500 220 4.3G0 

Interpole 40 525 230 2.900 

Non-interpole 37% 535 220 3,070 

The two motors of a size were coupled together, and the one 
not being tested was used as a generator for load. This had the 
additional advantage of operating both motors with the same 
inertia load, an important point in tests of this type. The usual 
type of magnetic control was used, so that the interval the cur- 
rent was off between "run" and "reverse" was essentially the 
same as in actual practice. 

Referring to Fig. 54, it will be seen that the interpole motor 
commutated a peak load of 320 per cent normal load at 80 per 
cent of the full-load speed, and that increasing the speed to 200 
per cent of normal decreased the maximum peak only to 270 
per cent full-load current. On the other hand, while the non- 
interpole motor commutated 270 per cent full-load current at 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 131 

80 per cent speed, it commutated only full-load current at 200 
per cent speed. 

In addition to the foregoing tests a cycle test was run to deter- 
mine the effect of plugging on the two types of motors. The 
same general scheme of connections was used, except that all 
operations were controlled by a motor-operated master drum. 
The cycle of operation was start, run under load, and plug, 
this being carried out on each motor alternately. This cycle 
was repeated approximately 7500 times on each test, each cycle 



200 






































\ 






ISO 






o 












^ 

3 




T5 

V 

» ./-/-s 






\-z. 
\ \ 

Vz. 










I* 
1 ° 




q.160 

CO 
















4->— 




c 

E 








o 










T ^ 




ouiO 
t 

s 








\"5. 


> 








v^ 5 










\ ■> 





































100 
































































80 


1 


00 


1 

Per 

( 


50 
Cen 
Mlov\ 


tFul 
rable 


00 

I Loo 
onf 


Z 

d Arr 
luggi 


50 


3 


00 



Fig. 54 — Relative Effects of Interpole and Non-interpole Motors 



requiring about thirty seconds. At the end of this time it 
was found that the commutator of the interpole motor had 
acquired a good polish and showed no bad effects from being 
plugged at 150 per cent speed with a peak of approximately 275 
per cent full load. The non-commutating-pole motor, however, 
did not show up so well as indicated by the curve in Fig. 54, as 
the commutator began to show signs of pitting, due to plugging 
peaks of slightly more than full load, the speed and number of 
cj^cles being the same as for the other motor. This test was con- 
ducted on several different sizes, the results being very much the 



132 ELECTRICAL AIDS TO GREATER PRODUCTION 

same in each case, showing that the interpole is extremely desir- 
able in motors which are to withstand severe plugging service. 

USE OF LIGHT-WEIGHT MOTORS A MEANS OF 

ECONOMIZING 

Economy with all the resources of the country is of the great- 
est importance under the present conditions, it being just as 
important to economize with copper and steel as it is to econo- 
mize with food and coal. In order to pay off the immense war 
debts it will be imperative for this country to make the best 
possible use of its resources. Of these copper and iron ore form 
very prominent parts. Economy in these metals must be made 
at every point, and no part of a machine should contain metal 
not necessary for its proper operation. By giving preference to 
lighter motors of equal rating users will encourage manufac- 
turers to seek out means of economizing metals and thus release 
a very substantial amount for other uses. 

Records submitted by A. Brunt of the Westinghouse Electric 
& Manufacturing Company indicate that the average-size direct- 
current general utility motor sold has a torque of 65 ft. -lb. 
(8.97-kg.-m.), corresponding to 15 hp. at 1200 r.p.m. This size 
of motor can be bought with a weight varying between 605 lb. 
and 1080 lb. (274.4 kg. and 489.8 kg.) (Fig. 56). Assuming the 
average weight of motors of 65 ft.-lb. (8.97-kg.-m.) torque to be 
845 lb. (383.3 kg.), and further assuming a total production in 
this country of 30,000 motors per year, the waste of material by 
using the average motor instead of the lightest motor will be 
(845 — 605) X 30,000, or 7,200,000 lb. (3,265,865 kg.) per year. 
This figure is appalling, especially under the conditions which 
exist at the present time. 

Improvements in the design of direct-current motors — chiefly 
the adoption of the commutating pole, a more thorough knowl- 
edge of allowable operating temperatures and more effective 
means of ventilation — have made it possible for progressive 
manufacturers to reduce the weight of their machines very sub- 
stantially (Fig. 55). 

Since all manufacturers sell in the same market, their prices 
for motors of the same rating must necessarily be nearly the 
same. The purchaser of a motor naturally will ask, ''Should I 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 133 

buy the light or the heavy motor?" The motors will all be 
designed to have the same temperature guarantees, and, assum- 
ing that the speed characteristics will be satisfactory and the 
efficiencies equally good, it may be asked, What are the advan- 
tages of the one over the other? 

Naturally many purchasers of direct-current motors will think 
that by buying the heavy motor they are getting more for their 
money. A careful comparison of the two motors, however, will 
show that this is not so. If the heavy motor should have more 
excess capacity, this should also show itself in dimensions of 
shaft and bearings. However, an examination of the pulley-end 



4000 
3500 

3000 

r> 
'2500 

i 
2000 



0(500 
D. 



1000 



500 

















a/ 


















// 




































r 




















1 


















r c 


9 








& 








v> 


<?/ 






i? 


,/ 










$/ 






flj£ 


y 












*j 
















,4 
















A 


/ 
















f 


































/ 




















// 





















3000 

eaoo 

2600 

2400 

2200 

£2000 

f 1800 

^ 1600 

a 1400 

,nl200 

g 1000 

°- 600 

<&00 

400 

200 















c / 


' i 



















/ 


/ 














i 


' , 


/ 




A 








? 




r 


h 


1 














/ 


J?t 


/ 
/ 












! 




V 


//, 














/C 


'/ 


'A 


V 












4 


' / 


A 


</ 














\\ 


{< 


















/ 


4) 


















Yk 




















f 


















A 





























































100 200 300 400 
F-o<?t-Pounds ; Torque 



500 



100 200 300 400 500 
Foo+-Pounds ; Torque 



Figs. 55 and 56 — Relation Between Weight and Torque foe Commu- 
tating-pole and non-commutating pole motors; also for seven va- 
RIOUS Makes of Motors 



bearing diameter for two competitive lines of motors manufac- 
tured by prominent concerns shows that there is very little dif- 
ference between shaft diameters of competitive motors. 

The lighter motor necessarily must be the better ventilated 
one, which means that the motor is so constructed that the cool- 
ing air comes in thorough contact with those internal parts in 
which the heat is generated. Thus it follows that the excess of 
actual external temperature over the temperature measured by 
applying a thermometer to outside surfaces must be smaller in 
the light, well-ventilated motor than in the heavy motor, with 
consequent smaller clanger to the insulation. In this respect the 



134 ELECTRICAL AIDS TO GREATER PRODUCTION 

light, well-ventilated motor is much to be preferred over the 
heavier one. 

Light motors further can be handled more easily and also 
have a lower freight rate, which is an advantage to the purchaser 
in case the motor is to be shipped outside of a free-delivery zone. 
That great weight is not necessarily an equivalent of superior 
qualities is well illustrated by the weight curves of Fig. 55. 
Efficiency and especially commutation of the commutating-pole 
motor are decidedly superior to the same qualities of the very 
much heavier non-commutating-pole motor. 

INDUSTRIAL MOTOR CONTROL 

In certain respects motor-controlling devices have been simpli- 
fied greatly since the early days of the art. In the beginning 
the electric motor was a peculiarly tender piece of apparatus 
both electrically and mechanically. The control of sparking was 
very imperfect, the insulation was none of the best, the slotted 
armature was unknown, and above all the motors in small sizes 
were commonly installed on lighting circuits of meager capacity 
so that their effect was unpleasantly conspicuous. Under such 
circumstances motors had to be installed where the brushes could 
receive constant attention, a precaution doubly necessary if any 
attempt were made to introduce variable speed. The starting 
rheostat had to be provided with many steps, and it behaved 
rather badly at that. Remote control, current-limiting devices 
other than open fuses, sometimes replaced by wire nails, and 
low-voltage automatic stops were quite unknown. 

The complicated starting rheostat can now be brought to a 
most elementary form, even down to a single step of resistance 
variation, and it is indeed not very unusual to omit the external 
starting resistance entirely. It is well to look a bit into the 
cause of this now justifiable change in practice. In the first 
place, direct-current motors are much better designed with re- 
spect to sparking than they were in the old times. A first-class 
modern motor will stand all kinds of speed changes and changes 
of load with never a blink at the brushes, so that rheostatic con- 
trol to avert commutator trouble at starting or in changing 
speeds is rather unnecessary. Second, the individual small 
motor is so trivial an element on the average electric system that 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 135 

it can be switched on or suddenly loaded without any perceptible 
effect on the system. A 10-hp. motor across the outside of a 
three-wire system is no longer a cause of worry to the station 
operator or to its own operation. This is one of the beneficial 
results of sheer magnitude in the scale of operations — that it 
takes 100 hp. or so to bear the same relation to the system opera- 
tion as 5 hp. or 10 hp. a quarter century ago. Again, those who 
buy and use motors are much less fussy about some of their 
characteristics than in the early days. 

Starting Induction Motors. Control of induction motors is 
a subject of very direct practical importance on account of the 
almost universal use of the induction motor for a very large 
variety of work. It is only in cases involving for the most part 
delicate speed control that the direct-current motor has intrin- 
sically any special reason for being, although, of course, it is in 
many localities the only form of motor for which power can be 
obtained and is now, as it always will be, extremely useful. In 
starting induction motors practice has been very widely modified 
since the early days of the art. In the beginning the induction 
motor had to make its way against the most violent, not to say 
abusive, kind of competition, during which period all kinds of 
absurd things were required of it, things which no man con- 
temporaneously dreamed of asking of a direct-current machine 
in regular service. The average central station twenty-five years 
ago was small in output and had meager copper in its distribut- 
ing system. A high call for current at starting, particularly 
current very badly out of phase, was so serious a matter- that 
early designers of induction motors were put to it to deal with 
the starting load in such manner as not to offend the delicate 
sensibility of the central-station men, stirred up to hypercritical 
caution by salesmen of direct-current apparatus. All that has, 
of course, now gone by with the overwhelmingly great use of 
alternating current, and the huge increase in station capacities 
makes a starting load of well-designed motors a relatively trivial 
matter. 

So it has come about that simple and effective automatic start- 
ing apparatus has come into use for induction motors of a kind 
which could not have obtained a hearing, much less commercial 
acceptance during the unnecessarily fussy period referred to. 
Small motors, unless they have to develop exceptionally large 



136 ELECTRICAL AIDS TO GREATER PRODUCTION 

starting* torques, are almost universally slammed on the lines 
with no more ceremony than one would exercise in turning on a 
bank of lamps. For larger motors some reasonable precautions 
are still in order. The larger squirrel-cage motors are custom- 
arily started at reduced transformer voltage by the use either of 
dead resistance or of the "autotransformer" or "compensator" 
device. The resistance type of starter, very simple and cheap, is 
commonly employed with resistance in two only of the three 
leads. In good old times the very suggestion of this would 
have shocked the manufacturer and produced long and violent 
discussion in the columns of electrical papers. However, it 
works admirably with small loss of efficiency and great conven- 
ience. TVhen the starting current is dropped below a predeter- 
mined point the automatic starter cuts the motor squarely over 
on to the supply mains, and that is the end of the matter. 
Starting at reduced voltage from some variety of auto-trans- 
former is the method very commonly applied to the larger 
squirrel-cage machines. In its original form the motor was 
started on the low voltage and thrown over at somewhere near 
the proper point by a manual double-throw switch. This left 
rather too much to the discretion of the operator, and automatic 
controllers have in considerable measure come into use. 

It has been found desirable to introduce certain devices to 
protect the insulation by disconnecting the low-voltage connec- 
tion entirely after the motor is up to speed and by keeping the 
motor in circuit during the passage from low to high voltage by 
the use of a protective inductance or resistance to save the 
transformer. Very excellent automatic starters of such type are 
in use and have been evolved for convenient push-button control 
in which the operator can start the train of operations from one 
or several points distant from the motor. The slip-ring motor 
with round rotor is the form widely used in cases where the 
starting torque is great and the motor of considerable size. 
Here, too, unbalanced secondaries are not infrequently used 
except in extreme cases of demand for torque, inasmuch as the 
apparatus is thereby simplified, and the operation appears to be 
entirely satisfactory. A well-designed controller, operating au- 
tomatically on the secondary resistance, brings the motor up to 
speed with ample torque and great smoothness, although for cer- 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 137 

tain special cases manual control still holds an important place. 
Altogether, the problem of easy and convenient starting for in- 
duction motors has been admirably solved, so that in point of 
fact nobody thinks seriously about it at all, but simply installs 
the type of starter which seems most convenient for the case in 
hand. 

Speeding Shopwork with Automatic-Control, Adjustable- 
Speed Motors. Time and labor as measures of production cost 
have become so important in the Union plant of the Bethlehem 
Shipbuilding Corporation at San Francisco that extensive 
changes in equipment have been made to speed up the rate of 
doing work and decrease the labor required. Many of the older 
machine tools have recently been provided with automatic con- 
trol or equipped with new adjustable-speed motors outright. 
Experience with these improvements has been such that the 
new machine shop has been equipped throughout with adjust- 
able-speed direct-current motors with dynamic brakes and en- 
tirely automatic control. 

Although all the equipment has not yet been installed, there 
are now about 100 motor-driven machine tools in service in the 
shop. The motors are all sizes ranging up to 35 hp., the total 
installed capacity being about 500 hp. The shop schedule is 
such that no equipment is allowed to stand idle except when 
repairs are necessary. As soon as new tools are received they 
are put in service immediately. 

The direct-current equipment and the automatic features are 
working out very satisfactorily. With about thirty speeds ex- 
tending over a ratio of four to one and controlled by conveni- 
ently placed push-buttons, operators work much more effect- 
ively than where only four speeds could be attained, and that 
with some effort in shifting pulleys. Moreover, the dynamic 
brake brings the work to a stop so quickly that time is saved in 
the inspection and the operator is inclined to examine it more 
frequently. Foremen regard this is a most important factor in 
speeding up the work, and the workmen themselves prefer it 
because of its "convenience." The automatic control gives a 
fixed rate of acceleration. 



138 ELECTRICAL AIDS TO GREATER PRODUCTION 

MACHINE-TOOL DRIVE 

The use of motors has steadily increased with the improve- 
ment of their applications and the general availability of elec- 
tric power until today the majority of new equipment of the 
heavier sort is fitted for motor drive. Its fundamental advan- 
tages of convenience, efficiency, flexibility and exact speed con- 
trol are well known. The objections on the score of high first 
cost, the price of power and the conservatism that clings to old 
methods have been steadily fading from view. From now on, 
as new shops are equipped, the motor is surely coming into its 
own. Heretofore there have been the inconvenience of changing 
over machines for individual drive and the natural objection to 
scrapping equipment in good condition. Moreover, in an old 
shop fully organized for belt drive many of the characteristic 
advantages of motors cannot be fully realized. In starting 
afresh the whole layout of the shop can be planned for maximum 
efficiency without having to consider the necessities of arrange- 
ment from the viewpoint of the transmission of power by belts 
and shafts. 

Group Versus Individual Drive. Speaking broadly, a ma- 
chine in which the item of power consumption is a considerable 
one in the cost of product should be individually motor-driven 
merely on account of the increased efficiency. If, as very com- 
monly happens, exact speed control exercises an important influ- 
ence on its rate of output — that is, on the working efficiency of 
the operative — individual drive with its complete power of 
speed control is doubly necessary. Only with light machines 
steadily worked in groups at fairly uniform output can group 
driving be really advantageous. It is the working unit, whether 
of one or half a dozen machines, that must be considered. At 
the present moment the amount and character of overtime work 
is a peculiarly important item. With individual drive certain 
combinations of machine tools necessary to production can be 
made at will without reduction of efficiency from the power 
standpoint, while with belt and shaft drive as generally found 
full efficiency can be obtained only when the plant is in full 
operation. Most important of all, however, is the influence of 
individual motor drive on shop layout and working organiza- 
tion. When every machine has its own separate motor, not 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 139 

only can the plant be kept more clearly and better lighted, but 
it can be arranged for the highest efficiency of production irre- 
spective of all considerations of power supply. Machines can be 
grouped and placed so as to insure the minimum of back-lash in 
that steady movement of materials, processes and finished work 
that is so necessary to high output at a minimum cost. 

Mere saving of time due to speed and ease of control and to 
the placing of machines so as to call for the least human effort 
in handling the work is no small practical item of gain. Like- 
wise, the abolition of shafting, belting and all overhead 'gear 
leaves the space clear for the cranes and travelers needed for 
the easy transference of heavy products without interference 
with the floor space and often with the workers as well. In 
fact, it is these operative advantages, quite aside from the sav- 
ing of power, that constitute the strongest reason for going to 
individual motor drive in all new installations. 

Thus, the advantages of individual drive are in lessened con- 
stant losses in the power supply, in extremely facile control and 
in the independence which may be secured in the placing of 
various machines. The contrary factors are enhanced first cost 
of individual motor drive, particularly in machines requiring 
motors of small output, and the consequent gain from dispens- 
ing with separate motors altogether in the cases where a number 
of machines are operated simultaneously like a unit and prac- 
tically at full load. There are also collateral advantages from 
belt drive including a number of machines in cases where each 
individual machine is subject to extreme changes of load which 
in case of a separate motor would require such high overload 
capacity as to increase the cost and decrease the efficiency. The 
friction losses due to shafting in an ordinary machine shop are 
rather large — at least 25 per cent on the whole, and often 30 
per cent. This therefore gives a reasonable opportunity for 
actual saving of power by the use of individual motors. 

In the somewhat exceptional cases where the power cost of an 
operation is a very material factor this saving might of itself be 
enough to justify the individual drive, but there is very much 
to be said for the separately driven machine merely from the 
standpoint of that flexibility which means increased output. 
Anything which can cut down the relative importance of the 
element of human labor should in these days be sought ear- 



140 ELECTRICAL AIDS TO GREATER PRODUCTION 

nestly, and if by the use of carefully regulated electric drive 
the speed of operations can be increased and the finished product 
delivered with less time spent with the laborer, there is a very 
definite gain irrespective of whether the work is piece work or 
day work. In the one case there is, of course, a direct saving in 
cost of labor, in the other an indirect saving by that increased 
production which raises the efficiency of the whole shop. 

The balance of the argument therefore stands in a large per- 

TABLE XXI— DATA ON MACHINE GROUPING AND POWER 
REQUIREMENTS IN A LARGE SHOP 





Motor 




Machines 






Group 














No. 


Hp. 


No. 


Kind 


Size 


Hp. 


Remarks 


1 


15 


31 


Shaper 


24 in. x 14 in. 


2 








30 


Shaper 


24 in. x 11 in. 


2 








32 


Drill press 


y>in.-3 in. 


1 








42 


Planer 


12 ft. x 4 ft. 


15 








G5 


Planer 


12 ft. x 3 ft. 10 in. 


15 








7 


Borer 


8 in. 


1 








43 


Drill press 


y 2 in.-3 in. 


1 




2 


5 


28 


Planer 


6 ft. x 1 ft. 


3 


Cylinders 






40 


Shaper 


15 in. x 10 ft, 


2 








33 


Drill press 


% in. -3 in. 


2 








18 


Lathe 


12 in. x7 ft. 


1 


Shaft 


3 


5 


8 


Lathe 


10 in. x 4 ft. 


% 


Turret 






37 


Emery wheel 


Sin. 


1 








71 


Surface grinder 




1 








38 


Drill press 


y 2 in.-2y± in. 


1 








G8 


Sandstone 




1 








13 


Lathe 


9 in. x 4 ft. 


% 


Prentiss tool 


4 


3 


10 


Lathe 


12 in. x 4 ft. 


1 


Shaft 






69 


Grinder (cutter) 




1 


Garvin 






70 


Grinder (cutter) 


^4 in.-l in. 


1 








46 


Drill press 




y 2 








45 


Drill press 


*4 in.-l in. 


y 2 




5 


10 


39 
57 


Drill press 
Auto screw cutter 


in-1 in. 


y 2 
5 








58 


Auto screw cutter 




5 


Jones & Lamson 






72 


Saw 


14 in. 


1 


Bars and shafts 


6 


5 


73 


Saw 


14 in. 


1 


Bars and shafts 






74 


Saw 


14 in. 


1 


Bars and shafts 






47 


Pipe cutter 


3 in. 


3 


Threads 






48 


Pipe cutter 


4^> in. 


3v 2 


Threads 






66 


Punch press 




1 





J 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 141 





Motor 




Machines 




Group 










No. 


Hp. 


No. 


Kind 


Size 


Hp. Remarks 


7 


5 


7 


Gear cutter 




5 


8 


10 


2 


Lathe 


33 in. x 9 ft. 3 in. 


iy>2 Drum boring 






12 


Lathe 


18 in. x 1 ft. 


5 Upright turret 


9 


10 


1 


Lathe 


36 in. x 14 ft. 


10 Large 






4 


Lathe 


24 in. x 9 ft. 


5 Drum turning 


10 


7% 


35 


Drill press 


^4 in.-l 1 ^ in. 


y 2 






25 


Lathe 


8 in. x 1 ft. 


y 2 Screw 






24 


Lathe 


10 in. x 2 ft. 


1 Turret 






14 


Lathe 


12 in. x 2 ft. 


1 Turret 






44 


Emery wheel 




1 


11 


10 


3 


Lathe 


24 in. x 11 ft. 


5 Crankshaft 






6 


Lathe 


18in.x 6 ft. 


2 Winch turning 






5 


Lathe 


22 in. x 1 ft. 8 in. 


3 Gear turret 






07 


Wet emery wheel 




1 






29 


Slotter 


10 in. 


5 






56 


Drill press 


V 2 in.-2 in. 


v-i 






55 


Miller 


4 ft. x 1 ft. 


10 






9 


Lathe 


11 in. x 13 ft. 


1 Shaft 






15 


Lathe 


10 in. x 5 ft. 


y 2 Shaft 






10 


Lathe 


8 in. x 4 in. 


y 2 Shaft 






20 


Lathe 


12 in. x 18 in. 


y 2 Shaft 






17 


Lathe 


13 in. x 7 ft. 6 in. 


1 Shaft 






19 


Lathe 


11 in. x 8 ft. 


y 2 Shaft 


12 


15 


11 


Lathe 


10 in. x 8 in. 


y 2 Shaft 






36 


Miller 


4 ft. x 1 ft. 


10 Shaft 






41 


Crank Press 


8 in. 100 tons 


1 Shaft 






49 


Miller 


4 ft. x 1 ft. 


10 






50 


Miller 


4 ft. x 1 ft. 


10 






51 


Drill press 


J/i in.-l}4 in. 


y 2 






52 


Grinder 


5 in. 


1 Emery 






53 


Slotter 


10 in. 


5 






54 


Grinder 


5 in. 


1 Emery 


13 


10 


21 


Lathe 


9 in. x 5 ft. 


1 Shaft • 






22 


Lathe 




1 Shaft 






23 


Lathe 


8 in. x 4 ft. 6 in. 


1 Shaft 






26 


Lathe 


8 in. x 3 ft. 


1 Shaft 






27 


Lathe 


8 in. x 4 ft. 6 in. 


1 Shaft 






59 


Saw 


24 in. 


5 Circular blocks 






75 


Drill press 


2 /4 in. to y 2 in. 


y 2 Circular blocks 


14 


7M> 


50 


Saw 


24 in. 


5 Circular blocks 






61 


Lathe 


42 in. 


2 Pattern turning 


15 


7% 


62 


Saw 


12 in. 


1 Pattern 






63 


Planer 


15 ft. x 1 ft. 6 in. 


3 Patterns 






64 


Saw 


3 ft. 


3 Band 



142 ELECTRICAL AIDS TO GREATER PRODLXTION 

centage of cases in favor of the individual drive, save in the 
operation of small and homogeneous groups of machines under 
nearly constant load and a few exceptional cases of extremelv 
variable load. 

Power Requirements of Machines in Large Shops. In the 
table on pages 140 and 141 are given the power requirements and 
best grouping of machines in a large machine shop that was re- 
cently laid out. The shop is divided into fifteen groups, the 
table giving a description of the driven machines as well as the 
horsepower of the motor required to drive the apparatus. This 
table should prove of value to engineers grouping machines for 
motor drive. The machines have been so arranged that for 
most jobs raw materials will enter the rear of the shop and pass 
from group to group, leaving the last group as a finished 
product, 

Motor-Driven Planers. The planer is one of the most impor- 
tant of machine tools and in some respects the least efficient 
from the standpoint of output, since at best only half of its 
motion is taken up in cutting, as opposed to the works of lathes 
and milling machines. The first requirement, therefore, of a 
scientific drive is that it should operate on the cutting stroke at 
the speed of maximum efficiency for the particular metal and 
the cut in hand, and that it should get back for another stroke 
in the minimum possible time with as little fuss and strain on 
the equipment as is practicable. 

The actual work required in making the cut is a comparatively 
small part of the cost of the whole planing operation, so that 
power economy itself is a less important item here than in many 
other machines. To meet the requirements of the particular 
cycle of operation necessary two general schemes are in use. 
The first of these provides an independent motor drive of the 
planer, using the ordinary belt equipment and eliminating the 
line shafting. In this case the motor runs at constant speed 
and the ordinary belt-shifting device takes care of the varying 
speed required in the cutting stroke and of the swift return 
necessary. It is not unusual to accelerate the return by auto- 
matic change in the field resistance. The obvious difficulty with 
the arrangement is the heavy demand for power and the severe 
strains imposed during the mechanical reversal. 

Of late planer manufacturers have been looking with more 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 143 

and more favor on the purely electric drive with reversing 
motor, using dynamic braking to take up the shock of the neces- 
sary reversals. A complete electric drive, of course, gives all 
manner of opportunity for proper speed variation, at the cost 
of somewhat more complicated and costly motor equipment. 
The chief advantage gained is a greater degree of flexibility and 
the practical abolition of the very severe strains arising from 
inertia of rotating parts. The inertia of the moving platen is 
small and that of the rotating parts is relatively very high, 
causing a corresponding violent effort in reversal. With the 
dynamic braking possible in the directly driven equipment this 
difficulty is greatly reduced, and when properly adjusted the di- 
rect-driven planer ought to be able to do the work with less wear 
and tear than if belting were employed with a continuously run- 
ning motor. The balance of cost in the two cases is not alto- 
gether easy to figure out, but experience with other electrical 
drives would indicate that the increased smoothness and flexi- 
bility of control with the reversing-motor equipment is well 
worth the while in standardized operations where workmen can 
be taught to use habitually the most efficient speeds. And in 
this, as in many other similar cases, it is output which counts 
as the largest item in successful manufacturing, especially when 
costs of material and labor are running to exaggerated figures. 

Minimizing Load with Group Grinder Drive. If the work 
cycles of grinding machine are arranged so they overlap and 
they are started in succession to take advantage of their fly- 
wheel effects the motor driving a group of them can be rated 
much lower than would otherwise be necessary. Starting the 
grinders is particularly beneficial because they have considerable 
inertia which would demand a very large starting current if all 
were started together. An investigation along this line, made 
by Sydney Fisher, is given in what follows: 

The drive consisted of twelve Hemming grinders, each ma- 
chine having a cup-shaped emery wheel 16 in. (40.6 cm.) in 
diameter with a radial thickness of 1.25 in. (3.2 cm.) and ope- 
rating at a speed of 625 r.p.m. The work feed is 1 ft. (30.5 cm.) 
per minute. Originally a 35-hp. motor was installed to drive six 
machines, but this motor was finally used to drive all twelve 
machines. 

The machines are arranged in groups of six, each of which is 



144 ELECTRICAL AIDS TO GREATER PRODUCTION 

operated by one man. The method of operation and the rate of 
feed is snch that the power demand gradually increases to a 
maximum when all six machines are grinding simultaneously, 
and then gradually decreases to a minimum when the machines 
have finished grinding. 

The two portions of the accompanying curve marked A and B 
indicate the variation in power demands under two different con- 
ditions of operation. During the period marked A the relative 
operation of the two groups is such as to cause their work cycles 
to be exactly in phase, while during period B they overlap. As 
shown by the curves, there is a marked difference in the power 
demand for the two conditions. 




*.---20 Mm.—>~ * ?--20 Mm. >] 



Fig. 57 — Load Curve with Grinders Operating Under Different 

Conditions 



AYith loading A the average power is 30.8 hp., which is less 
than the rated output of the motor. The peak load is 54.6 hp., 
which is well within the maximum overload capacity of the 
motor. The minimum load is 12.85 hp. Evidently there is 
quite a variation in power demand. 

The average power with B operation is 30.8 hp., the same as 
that for A, the work done in each case being practically the 
same and the periods equal (twenty minutes). The variation 
in power demand is considerably less and approaches the ideal 
condition of a uniform load of 30.8 hp. 

With intelligent operation as exemplified in B excessive cur- 
rent variation is obviated and higher operating efficiency is ob- 
tained. Most important of all is the lessened possibility of in- 



MOTOBS, CONTROL, SPECIFIC APPLICATIONS 145 

terruption of service due to tripping of the overload relays with 
excessive overload. 

Automatic Guard for Drill Presses. An automatic guard for 
drill presses was recently built for use in the plant of the Com- 
monwealth Steel Company of Granite City, 111., after one of the 
operators had been killed. This guard extends horizontally just 
above the drill table so that when struck or touched the main- 
line switch to the drill motor is opened, thereby causing a 
dynamic brake to stop the drill in one-quarter of a turn. This 
is practically instantaneous as the speed of the drill is 150 r.p.m. 




Wood Pin 



M Carbon 
\jj\Brushes 



Slate 

Attached 
to Machine 




Side Vieiv,Line Switch 



Iron o/- — pi andThrovYOpen,DCIosed 



Shuni Field 

\smmA 




Armature 



Fig. 58 — Abrangement for Stopping Drill Quickly 



All of the machine operators are instructed in shutting down 
the machines to do so by applying the dynamic brake by touch- 
ing the guard instead of walking to the switch box and opening 
the circuit manually. In this way they become so accustomed 
to using the dynamic brake that in case they were pulled into 
the drill at any time it would be almost second nature to them 
to strike the guard in some way. By examining the diagram, Fig. 
58, it may be observed that the release rod merely opens the main 
switch and short-circuits all the motor leads. The device was 
perfected by William Schnieder and H. E. Howey. 



146 ELECTRICAL AIDS TO GREATER PRODUCTION 

PLATE-SHOP DRIVES 

Factors governing the selection of motor drives, the rating re- 
quired and some of the characteristics which were desired for 
driving the plate-shop equipment of the Staten Island Ship- 
building Company are discussed in what follows by David Blwell, 
electrical engineer for Lockwood, Greene & Co. 

Since it was necessary to put this shop in service as soon as 
the building was up, and as the question of electric power supply 
for the whole plant had not been worked out at that time, the 
220-volt direct-current energy then available was used. The 
machine tools listed in Table XXII were installed and equipped 
with individual motors, in most cases belted directly to the 
machines. 

Conditions Influencing Drive. Every consideration involved 
in connection with the plate-shop machines led to individual 
drives. Neither the type of building, the arrangement of ma- 
chines nor the operating conditions surrounding the use of them 
made group drives desirable. 

The building is a high-studded steel-frame building with, peak 
roof and two longitudinal bays, with a traveling crane in one of 
them. Under these circumstances the shafting necessary for 
group drives would be cumbersome and expensive. Further- 
more, in order to secure sufficient space around the machines for 
handling the large plates and angles that are being fabricated 
considerable clearance had to be left between machines. This 
would further add to the expense of providing group drive. 

The other controlling factor is the fact that while the final 
product of the yard may be standardized (i. e., a number of 
identical vessels) on a given contract, each machine tool is used 
for several operations. The work on any given machine is, 
therefore, very much of a "jobbing" proposition, and the use of 
any machine is required for long or short periods at indefinite 
intervals. To give the greatest flexibility of service, maximum 
utility and the lowest power cost for the output involved indi- 
vidual motor drive was therefore chosen without question'. 

The arrangement of tools in the plate shop and routing of 
materials to and from other buildings is shown in the diagram 
of Fig. 59. The demand for immediate operation was so 
pressing that no opportunity was offered for any testing, and 



Ph 

O 
Q 

o 

I— I 
Q 
fi 
P 
M 
Ph 

fi 

< 

fi 

w 

I— I 

fi~ 
H 

GO 

o 

I— I 
H 
<! 
O 



H 
O 

w 

o 

w 

w 

H 
Ph 

o 
«! 

H 
«1 

Q 



H 



•cItt 'piscr ranm 

■"-■^ X t NC3(M O ^ iO U5 iC U1 

-ix'bj^; pa^oadxa; ^ co 



T 9}0X 



fife 



H ^ 5) 

fl ° rr 

Pi 

w 



10 io 



fife 



i— I o 

"# oi 



!>■ CO 

Tj5 CO 



SUI5TJ0 V\ M - ^ £ " W - S^ 

.1 i¥\ cM -# CO CM CM <M <M CO c<l 

Q T ' • x o n >o Tfmioooo • io . o cm 

•OlITiniri'JJ o CM' M tJH r-i fH r-I CM* CM ■ r-I rH 'CM rH 



Q CM t-COCO^lO-COcO-CO t- 

.oUT^J'Blg co'ocM ©rnVoO^rH' * CO 06 ' t^ rA 

CM CM CM i-h i—i i— l 



co co to co 



O O CM CO 
CM* C<1 CO CM 



CO CO t^ t^ 

COhh 



a 


Td 




3 


OJ 




n 






CJ 


Si 


• pi 


0) 


o 


M 


P-> 


bJ 


X 


K-' 


S 


H 





P. m 
Q r ^ 

fn bo 



CJ <n 
* I " rH 



pi pi 
. fl " .5 

:r^ec^ 



<D <D CJ 

-2 c c o 

& cd Cd P3 

p p c p 



M^eS^M^i-f- 



<D CJ CJ 

cd cd cd 

o . . O . 

rP P P .=3 P 



.5 voo^c p 



.* 



cd 

,2 U 
o . 



CJ CJ JJJ 

— < p »i o 

Ph cd cd ^h 



0> cj m 

-rfpl-pj* 

rP PH P-rP & 
" P P fi 



.S.S-S-.S '.g.5-L.^ 

^> ^p JS vf • vac ^§5 ^ ^o v« 



-H 


^ 





CJ 


r^ 


f4 


ni 


^ 


d 


P 


■ rH 


u 



_ O 

— i jh -te 



uj *nimQ tjh t^l ^ 

o o o 
H J H cc o o 



1(5 h O N O O 

rH r-i CM 



'opI 

■P Ph 

.S.S 

CO o 



O O 



ia 



o i>- cm co co cm m m o 

OTtlOOl-^t^CO IO IO ^ 



•d H 



io io >o io 

COlOO CNNOON 



P fH 

cd a> 

'Hncd 



2 s 

P . 



0) TO 



^P 



0) 

.s 



^£^cm ^ 

Cd • rt P t fC< 



CM ^ 

J^i CO f-4 

03 O 
03 



?« cd 



p 

Pm' 



P 

Ph 



IO io 



cd cj 

■si. 

^p. 



o 



»o 






IO 

O) 

o 



o 

CO 



• a> 
. cd 

^'^ 
p jn 

s- 1 P 
£ cd 

o o 



.2 oic 



33 50,^ 



O 



o cd ° 

. i I— i i — I' — ' ^o 

!B 0) M 



=3c£ 



Ph 



O 

cu Jz 

o ai 






cd cd 



2 cd 
'P 
cd 



rP 






P^ ^ 



p 4) rP O X^i 1 



p 


CO DQ 


o 




1-3 


<^<3 


=3 


c^og 


02 




CJ 


be &J0 


r—i 


P P 


M 


o o 



> rP 

cd P 

•c ^ § 

o £ p 



03 


a 




bx 


l-H 


PI 


Ph cd 


p 


P 


"T 




»0^C0^ 




CJ 


cfi 




-4-1 


CI: 


cd 


Pj 


Ph 


cd 


p 


P 








to 


V.CI vH 

p>^ 



ONCO 



IO IO IO 
CM t^ CM 



IO IO IO 
CO t^ I>1 



ri4 O 

.s ° 

^ cd 

CJ .S 

S cd 

P Sh 

o 

cj to 



.3 o 
nd fe- 
ed -" 
u 
<u 

>,P 
cj ■•-} 

cd co 
=g bX) 

M P 
CJ rQ , 

Si CJ 

cj rp 
fife 



cd 

Pi 

P P fc JD 
K O P 

fi <H 



cp 



-p 



rP 
H 



•o^j aunp-B^ 



Cd CO tHH 



147 



O — i CMCO Tt^>0 CO t-- 



148 ELECTRICAL AIDS TO GREATER PRODUCTION 

the motor sizes were chosen with the idea of not having them 
too small even if they were too large. 

Soon after the building had been successfully put into service 
the question of permanent electric power supply for the plant 
was taken up, the old direct-current plant being entirely inade- 
quate for the requirements of the new yard and occupying a 
site needed for other buildings. A careful analysis of all power 
requirements led to a contract for alternating-current service 



>f-,f/.jfe 

ANGE SHEARS 

| 

7 i 

W- DP'LL PRESS 



To Sh/ptvays 



P I 

" ANGLE PUNCH 




To Rivet Shop 
and Shipways 

Ale 



■'-■PLANERS-- 



BENDING ROLL' 
i 



COUNTERSINKING 
MACHINE *•.. 
17 



ANGLE PUNCH 







COUNTERSINKING 
.-* MACHINES 



iM 



.BLOWER 




CH >§]I3 

GRINDER 



PUNCH 



To Mould Loft, Carpenters and Y 
Joiners Shop, Plate and Angle 
Bending Building and Plate Racks 



To Oate House, Tool Repair 
Shop, Power House. Boiler 
Shop and Machine Shop 



Fig. 59 — Layout of Machines in Plate Shop 



being entered into with the Richmond Light & Railroad Com- 
pany. 

The necessity of changing the motor drives from direct cur- 
rent to alternating current for operation on the purchased-power 
lines therefore afforded the opportunity for determining the 
actual duty cycle of work on the machines and the proper alter- 
nating-current motor to install. Ammeter and voltmeter read- 
ings were taken on the individual direct-current motors on each 
of the drives, with the results which are given in Table XXIII. 

Determination of Proper Rating. Considering the test data 
on the direct-current motors, item 1 is the conventional grind- 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 149 

stone and emery wheel used for sharpening the shop tools. The 
motor drives a small counter-shaft from which both grinding 
wheels are belted. This group was found to be considerably 
over-motored, a 2-hp. motor proving sufficient for the load. 

TABLE XXIII— ALTERNATING-CURRENT EQUIPMENT INSTALLED 
IN PLATE SHOP (STATEN ISLAND SHIPBUILDING COMPANY) 

A. C. Motors Installed 
Pulley 
Mach. • Full Load Diani- Starting 

No. Machine Hp. Type i R.P.M. eter, In. Device 2 

1 Grinders 2 S 1720 4.5 A 

2 Plate planer 10 S 1150 6.5 B 

3 Plate planer 15 S 1740 7.5 E 

4 Bending rolls .. . 25 S 1160 8.0 E 

5 Angle punch 5 SH 680 5.5 C 

6 Angle shears .... 5 SH 850 6.0 C 

7 Drill press 3 S 1730 5.0 D 

8 Blower 5 S 1735 8.5 C 

9 Punch 5 SH 850 6.5 C 

10 Shear 5 SH 680 5.0 C 

11 Punch 5 SH 680 5.0 . C 

12 Countersink ... 5 S 1730 4.5 C 

13 Punch 5 SH 680 5.0 C 

14 Countersink ... 3 S 1730 4.0 D 

15 Countersink ... 3 S 1730 4.0 D 

16 Shears 5 SH 680 5.0 C 

17 Angle punch ... 5 SH 850 8.0 C 

1 S = squirrel-cage motor, standard design ; SH = squirrel-cage motor 
with high-resistance end rings. 

2 A = three-pole, 250-volt, 30-amp., inclosed switch fused for 20 amp. ; 
B = three-pole, 250-volt, 100-amp. inclosed switch fused for 90 amp.; C = 
three-pole, 250-volt, 60-amp., inclosed switch fused for 50 amp. ; D = three- 
pole, 250-volt, 30 amp., inclosed switch fused for 30 amp. ; E = starting 
compensator arranged for conduit wiring with inverse-time-element over- 
load and no- voltage-release coils. 



The plate planers (items 2 and 3) have long beds, on which 
the plates whose edges are to be planed are placed, the plate be- 
ing held firmly by adjustable jack screws on the upper frame of 
the machine. The cutting tool is held on a carriage which 
travels parallel to the edge of the plate on a long screw. The 
tests showed that both the plate planers were considerably over- 
motored as then equipped and that 10-hp. and 15-hp. motors for 
items 2 and 3 respectively would be found to be ample. 



150 ELECTRICAL AIDS TO GREATER PRODUCTION 

The bending rolls (item 4) are for bending plate cold into 
circular shape, the relative location of the rolls being adjusted 
manually to increase the curvature as the plate is passed back 
and forth through the rolls. The motor is belt-connected with a 
counter-shaft from which open and crossed belts operated by a 
shifter drive the rolls in either direction. While the rolls were 
equipped with a 30-hp. motor, the tests indicated that a 25-hp. 
motor was proper for this drive. 

Instead of a 10-hp. motor on the drill press and blower (items 
7 and 8), 3-hp. and 5-hp. motors respectively were found of 
ample size. On the countersinks (items 12, 14 and 15) a 5-hp. 
motor for No. 12 and 3 hp. each for the other two were found to 
be suitable. 

Xo unusual starting conditions existed in connection with the 
foregoing drives. On some of them the motor is started light 
and the load applied by shifting the belt, and on others the tool 
starts directly with the motor ; but as there is little inertia to 
overcome on account of the absence of flywheels, etc., standard 
squirrel-cage motors were used. 

The most interesting motor applications are the punch and 
shear illustrations (items 5, 6, 9, 10, 11, 13, 16 and 17). They 
are low-speed machines and ones in which the working interval 
is very short, being simply the stroke during which the tool is 
punching or shearing. At that moment, however, the instan- 
taneous power requirement is very heavy. Rather than use a 
motor big enough to carry the tool through its working stroke, 
the machine-tool designers adopted the wise expedient of using 
a heavy flywheel, which stores up energy when the machine is 
running light and delivers it as the machine slows down on the 
cutting stroke. 

The presence of the flywheel permits a much smaller motor 
than would otherwise be required, but proper acceleration of the 
machine presents quite a problem. The severe starting condi- 
tions which resulted are indicated by the accompanying test 
data. 

Some Factors that Affect Selection. Three important points 
which have to be recognized in the selection of a motor are the 
power required to start the machines, that required to run them, 
and the maximum horsepower necessary which the motor can 
develop at starting without throwing off the motor belt. 



MOTOKS, CONTROL, SPECIFIC APPLICATIONS 151 

The tests indicated that 9 hp. to 12 hp. was necessary to start 
the punching and shearing machines. Since a standard squir- 
rel-cage motor of about the sizes required would only develop a 
starting torque equivalent to one to one and a half times full- 
load torque, it is evident that a motor of proper size to handle 
running conditions would stand no chance of starting these ma- 
chines under the conditions shown to exist. If the driving belt 
happened to be too loose, the motor pulley might slip and throw 
it off, but it could not develop sufficient torque to meet the start- 
ing requirements indicated by the test. If a starting compen- 
sator were used, it would lower the starting torque still further 
by reducing the applied voltage. For these reasons it was im- 
possible to use a standard squirrel-cage motor either with or 
without starting compensator. 

The proper drive for punching or shearing machines is there- 
fore one which gives a powerful yet gradual starting character- 
istic. This may be secured from an alternating-current motor 
with slip rings and external starting device or from a squirrel- 
cage motor with high-resistance and rings. From the standpoint 
of simplicity, price and quick delivery, the high-resistance end- 
ring type was considered preferable, as a number of manufac- 
turers carry a stock for elevator service. 

When this type of motor is thrown directly on the line the high 
resistance in the rotor end rings causes considerable slip at 
starting, allowing the motor to accelerate powerfully and yet 
gradually. Another advantage of the high-resistance type is its 
falling speed characteristic with increasing load, which results 
in an increasing torque and helps the flywheel over the peak of 
the load. The speed-torque characteristics of this motor are 
very similar to that of the series direct-current motor used for 
traction purposes, and they fit it admirably for this work. The 
greater complexity of the slip-ring motor and its susceptibility 
to trouble from dirt and grit in machine shops were other factors 
which affected the selection of high-resistance end-ring squirrel- 
cage motors for the punching and shearing machines. 

The only compensators in the shop are used on items 3 and 4. 
These were necessary, as the motors are rated in excess of 10 
hp., the compensator being used to limit the inrush of current at 
starting. 

On the other motors, because of their small size, no compen- 



152 ELECTRICAL AIDS TO GREATER PRODUCTION 

sators are necessary to limit the starting current, while on the 
high-resistance end-ring motors no compensation is permissible, 
as fnll line-voltage is necessary on these motors to give the 
proper starting torque. 

A motor voltage of 220 was chosen for the plant to secure 
maximum safety for the operatives. With this low voltage it 
was not necessary to use oil circuit breakers for starting the 
motors, so safety inclosed fused knife switches were chosen. 
The switch is opened or closed by a handle outside and offers 
complete safety for the operative. 

To take the large starting current of the squirrel-cage motors 
it was necessary to fuse their switches so heavily that no protec- 
tion is afforded to the motor at moderate overload. In case of 
grounds or dead short circuit in the motor, however, the fuses 
would cut it off. With individual motors on machines which 
are always under the eye of the operative there is little chance 
for overload on the motor which the operative will not know 
about. The plant was designed and equipped under the super- 
vision of Lockwood, Green & Company, Boston and New York. 

WOOD WORKING 

Woodworking is one industry in which the advantages of motor 
drive over shaft and belt drive are very marked. Electric drive 
is especially desirable because the machines can be located for 
the most convenient handling of the products and because long 
shafts will be required with group drive if the machines are 
scattered to permit the piling of stock and finished products. 
Furthermore, much of the machinery is used intermittently for 
comparatively short periods, resulting in considerable transmis- 
sion loss if shaft and belt drive is used. 

For driving wood-working machinery the induction motor pos- 
sesses such characteristic advantages that practically nothing else 
would be considered on its merits even were there a choice of 
direct-current and alternating-current service. The immunity of 
induction motors from the ill effects of dust and dirt, and free- 
dom from danger of fire through the misbehavior of a dirty com- 
mutator, form sufficient reasons for abandoning any machine 
that has a commutator. Only in very rare instances, where ex- 
treme variation of speed is required for special operation, has the 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 153 

direct-current motor any claim to consideration. Most wood- 
working machines are conveniently driven by motors of the squir- 
rel-cage type. If the squirrel-cage rotor has low slip it drives 
ahead with remarkably good speed regulation and so holds up 
the output. If only a small amount of flywheel effect is desired 
the same type of motor designed for larger slip meets the re- 
quirement, but wherever great flywheel effect is necessary it is 
generally thought desirable to install a slip-ring motor with an 
external resistance, preferably adjustable, to meet the require- 
ments of flywheel working, although a fixed resistance is fre- 
quently all that is necessary. The latter arrangement is a com- 
mon practice in operating the large handsaws for timber sawing. 
These saws may run at speeds up to 10,000 ft. (3048 m.) per 
minute and the band wheels themselves may weigh several tons. 
In such instances the flywheel effects are very powerful, and 
there must be heavy starting effort and reliance on stored energy 
to drive through peaks of load. 

With certain other classes of wood-working machinery, such 
as planing mills, cases also occur where the slip-ring type of 
motor with wound rotor is advisable on account of the necessary 
heavy starting torque. Push-button control, often from more 
than one point, is found to be a very important feature in the 
operation of certain machines, saving much time and electrical 
energy as well. 

Where Group Drive Was Advisable. The Riddle-Rehbein 
Manufacturing Company of St. Louis has laid out its drives with 
such care that practically all objectionable features of the ordi- 
nary wood-working plant have been eliminated and energy bills 
are less than for similar plants of smaller output, says W. A. 
Black, engineer with Fairbanks, Morse & Co. In most cases in- 
dividual drives are used, as with this method the motors remain 
idle except at such times as the machines are in use. 

In planning the drive it was found that there were certain 
places where individual drive would not be economical. For in- 
stance, a battery of nailing machines were arranged for group 
drive because a careful study showed that the load is intermit- 
tent and that seldom more than one machine is required to do 
actual work at any one instant. If individual drive had been 
used, a 2-hp. motor would have been required for each machine 
and the motor would have been loaded only intermittently, giv- 



154 ELECTRICAL AIDS TO GREATER PRODUCTION 

ing a very low load factor with its resultant low power factor 
and efficiency. With the arrangement adopted a 5-hp. motor 
drives a battery of five nailers, running with approximately 
steady load at approximately full load and giving a higher power 
factor and efficiency than the small machines even had they been 
operating at full load. 

Another factor influencing the choice of group drive was that 
in this work the machines are never operated as individual units, 
but each machine performs its part of a progressive operation. 
The machines are used for making boxes, two end machines being 
used for framing the boxes, the next two machines for nailing 
sides, and the center machines for nailing the bottom of boxes 
coming from each side. The boxes finished by center machine are 
loaded on a truck placed within reach of the operator. 

Value of Substantial Foundations. The 30-in. (76-cm.) 
double surfacer was direct connected to a 50-hp., 1200-r.p.m. in- 
duction motor. The planer and motor are mounted on I-beams 
embedded in a concrete foundation which extends through the 
basement into solid ground. Six hundred and fifty cubic feet 
(18.2 cu. m.) of concrete was used in the foundation, but the ex- 
pense of making it is well offset by the freedom from vibration 
and the perfect alignment maintained thereby. The advantage 
of a firm foundation cannot be overestimated, especially for 
direct-connected machines. The foundations should be large 
enough to accommodate both the machine and the driving motor, 
as failures have occurred where a machine and the driviDg motor 
were mounted on separate foundations, owing to foundations 
moving with reference to each other and thus throwing the ma- 
chines out of line. 

The advantages of a solid foundation for maintaining perfect 
alignment are well illustrated by the performance of a 54-in. 
(137-cm.) resaw, which was mounted on a substantial founda- 
tion and directly connected to a 35-hp., 600-r.p.m., motor. After 
being, in service over four years, the machine, with a tension of 
2000 lb. (907 kg.) on a saw, wouh 1 run for two minutes and 
thirty seconds after the power was shut off. With a less substan- 
tial foundation the heavy machine would have vibrated out of 
line and the strain on the bearings would have caused excessive 
repair expenses. 

Ball Bearings Reduce Maintenance. Direct-connected ball- 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 155 

bearing motors reduce the maintenance expense cost to a mini- 
mum. There are no belts to slip, break or be taken care of. The 
ball bearings are contained in dust-proof inclosures requiring 
only infrequent attention compared with other types. With 
such motors and bearings the greasy dust so prominent in most 
woodworking plants can be avoided. Furthermore, the absence 
of oil and grease on motor frame and windings makes it possible 
to clean the machines by blowing off the dry dust. For the pur- 
pose of cleaning machines the woodworking company has a small 
motor-driven air compressor which is in use only when the clean- 
ing is necessary. 

While machines which are belted to motors mounted on the 
ceiling have all of the advantages of individual drive, they have 
the disadvantage that the belts obstruct the light. In addition, 
since the belts are long, they require more attention and are 
harder to cover with protective guards. To overcome these ob- 
jections many of the motors in this plant were mounted on the 
ceiling under the driven machine and a belt was run through an 
opening in the floor. This arrangement had all the advantages 
of ceiling mounting and at the same time permitted the use of 
short belts that could be easily protected by guards. No changes 
were necessary in the bearing construction as ball bearings were 
used and only occasional attention is required. With this type 
of drive it was necessary to guard against the use of excessively 
short belts and against the location of motors directly under 
driven pulleys, as these conditions would reduce the area of con- 
tact of belt on pulleys. 

Vertical Shaft Motors for Shapers. A very practical drive 
was obtained for the two-spindle shapers used in this plant by 
belting them to two 3-hp., 1800-r.p.m., vertical motors. The 
starting switches are mounted on side of machine opposite the 
motor within reach of the operator. Either or both spindles can 
be readily started or stopped as required. The use of vertical 
motors eliminates the need of crossed belts, and the ease with 
which spindles can be started or stopped reduces the tendency 
for the operator to leave spindles in operation when not in use. 

On a small jig-saw used for cutting out ornamental work the 
lines of which have to be followed very closely a unique arrange- 
ment is used to keep the work free from sawdust. A small ball- 
bearing motor is belted to a blower, which in turn is connected 



156 ELECTRICAL AIDS TO GREATER PRODUCTION 

by flexible tubing to a nozzle placed close to the work. The air 
from the blower is forced through the nozzle, which blows all 
sawdust from the work and leaves the lines visible. With ball- 
bearing motors it is practicable to cover the motors as it is not 
necessary to remove the covers frequently for oiling. 

Dovetail Glue Jointer. A drive which required careful con- 
sideration before it was successfully worked out was that of a 
Linderman automatic dovetail glue jointer driven by a 15-hp.. 
1200-r.p.m. motor. In cold weather the high torque necessary 
to start required either a larger-size squirrel-cage motor or a 
motor of the wound-rotor type. With the larger squirrel-cage 
motor the starting current would have been objectionable and 
the power required would have only lightly loaded the motor 
after the machine had attained full speed. The wound-rotor 
type of motor with a secondary starter would have overcome the 
difficulty of operation but would have imposed the necessity of 
more care owing to slip rings, brushes and starter contacts. 

The drive was very successfully taken care of with an internal 
starter motor. With this motor it was possible to obtain a high 
starting torque with a low starting current in a reasonably short 
starting period. The starting switch was simply a single-throw 
switch, and slip rings and brushes were eliminated. The instal- 
lation has been in operation for over three years and has given 
perfect satisfaction. 

Value of Flywheels in Woodworking. Owing to the fluctua- 
tions in load obtained with certain kinds of woodworking ma- 
chinery, it has frequently been the practice to over-motor the 
machine in order to carry the peak loads. As a result the load 
factor, the power factor and the over-all motor efficiency have 
been detrimentally affected and more than the necessary outlay 
of money has had to be invested. 

In several instances David R. Shearer has found that the 
average load on a given woodworking machine is only 50 per cent 
of the installed motor capacity and that some load peaks run as 
high as 100 per cent above the motor rating. In other words, 
some peaks occur which are four times the average load. 

If the first cost of the motors were the only factor to be con- 
sidered, much larger motors than are demanded by the ma- 
chines might not be so objectionable ; but the fact that any motor 
operating much below its rating will not operate at its maximum 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 157 

efficiency throws a different light on the subject. In the case 
of induction motors the power factor decreases with the load so 
that the system may be seriously disturbed if the motors are un- 
derloaded, especially if fed by a small local or isolated plant. 
The highest efficiency is usually obtained from an induction 
motor at full-load rating and the highest power factor at slight 
overloads. With one standard motor of the induction type the 
efficiency dropped 2 per cent from full load to half load, and the 
power factor dropped 12 per cent with the same decrease in load. 
Below half load the results are still more serious. 



120 

L. 100 



.* 80 



■8k 



60 















































































< n 


Ithou t- Fly* heel 
•With Fly irheef / 


r 




\ 
























^ 




















jr 








L 


** 




h. 


















^ 








/Installed ■ 
Capacity' 





































































I 



23456789 
Seconds 



10 II 12 13 14 15 16 17 



Fig. 60 — Load Curve of a Gang-edger Operating on Green Lumber with 
and Without a 1500-lb. (680-kg.) Flywheel 

The motor driving this machine is rated at 60 hp. and is directly con- 
nected to operate at a speed of 1800 r.p.m. on 440-volt, three-phase energy 
supplied by an isolated plant. The operating conditions were practically 
the same in both tests so that the value of the flywheel can be readily ob- 
served. Without the flywheel the demand increased above the maximum 
capacity of the motor for an instant. It caused excessive heating and 
sometimes stalled the machine. After the flywheel was attached the motor 
was operated at a lower temperature and never stalled during periods of 
heavier cutting. . 



On account of the trouble experienced with some motor-driven 
woodworking machines in the past, some apprehension has arisen 
regarding the advantages of individual drive which should be 
dispelled, inasmuch as the trouble has generally been caused by 
improper application of the motor. So strong has been this ob- 
jection that in some instances the individual drive has been 
taken out and group drive substituted so that the machine peaks 
could be carried by the overload capacity of a larger motor. 
This method of drive may be the correct thing in some cases, 
but is less desirable than the individual drive on account of the 
necessary shafting and belting with the attendant losses in ef- 
ficiency. Furthermore, the group-drive motor may be subjected 



158 ELECTRICAL AIDS TO GREATER PRODUCTION 

to concurrent peaks (Fig. 61) which may pull it out of step, thus 
shutting down the whole installation and causing serious delay. 

The simplest and cheapest way to obviate pronounced peaks is 
to install individual flywheels on the motor shafts of each ma- 
chine and retain the advantages of the individual drive. With 
this arrangement the loads can be carried by motors considerably 
lower in rating than would be required if flywheels were not 
used, and in addition the motors will operate more nearly at 
normal load. Of course, the flywheel must be especially de- 
signed for each machine as the operating characteristics vary 
considerably. 

The duration of the cut and the period during which the ma- 

























1 








































A 


















u 




































1 






5 


































j 


y 






o_ 


/ 












■ •> 


V 


























to 


f 








































o 

c 





















































































Time 

Fig. 61 — Individual Power-demand Curves of Three Motors with the 
Group Demand Plotted Above 
None of these machines was equipped with a flywheel. The curves show 
that a concurrent group peak is possible which may require over-motor- 
ing of the group when flywheels are not used. In the plant at which 
these tests were conducted a total plant concurrent peak occurred on an 
average twice in ten hours. 



chine is running idle are the principal factors which should 
determine the flywheel effect necessary. As an example, the 
duration of a trimmer cut is very short, while the idle period is 
slightly longer. A slasher cut is similar to that of a trimmer, 
but considerably more power may be required when a butt slab 
is being cut. A gang-edger cut is considerably longer than 
either of the foregoing operations. A short interval exists be- 
tween cuts which must be taken into consideration in the design 
of the flywheel and in deciding upon the size of driving motor 
to install. 

Sometimes it is convenient to test the instantaneous power de- 
mands on the machine while operating it from a motor somewhat 
larger than is necessary. From these tests the average load and 
maximum peaks can be determined. If the test results are 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 159 

plotted as curves, it is comparatively easy to decide how many 
foot-pounds must be added to the motor power during peaks by a 
flywheel to bring the power demand on the motor down to a de- 
sirable value. During the period when the machine is not cut- 
ting the motor stores energy in the flywheel, which can later be 
used while the tool is cutting. 

Another factor to consider when using flywheels is the rotor 
resistance of the driving motor when it is of the three-phase in- 
duction type. As the rotor resistance is increased the slip will 
increase, allowing a greater reduction of speed under heavy load 
and thus permitting the flywheel to give up some of its stored 
energy. If the load surges are frequent and pronounced, this 
characteristic of the motor tends to minimize the line disturb- 
ances, but if the peaks are of long duration a high-resistance 
rotor will allow the speed of the machine to drop too low for the 
proper action of the cutting knives or saws. 

Machines on Which Flywheels Are Most Desirable. The 
woodworking machines on which it is most necessary and eco- 
nomical to install flywheels, when operated by individual motor 
drive, include circular rip and cut-off saws, edgers, trimmers, 
slashers, timber trimmers, some types of planers and flooring 
machines, "hogs, " and in general any machine which has peri- 
odic loads and periods of non-production. Flywheels are not of 
much advantage on band saws, because these machines usually 
have sufficient flywheel effect in the band wheels which carry 
the saw. 

As the friction load of any woodworking machine is prac- 
tically constant, it is advisable to determine this load first, then 
the average power necessary to do the actual cutting. These 
two factors will determine the motor size if a flywheel is used to 
reduce the peaks to a value which can be handled by the over- 
load capacity of the motor. 

As a result of the tests indicated by Figs. 60 and 61 and others 
made upon different woodworking machines Mr. Shearer has 
come to the conclusion that better results would be secured with 
individual drive by the more general use of suitably designed 
flywheels. The necessary generating plant capacity would be 
decreased, the size of the individual motors could be reduced, the 
load factor would be improved, the efficiency increased and the 
power factor raised. Furthermore, flywheels will relieve the 



160 ELECTRICAL AIDS TO GREATER PRODUCTION 

motors and starters from excessive stresses occasioned by the pro- 
nounced surges of power demand. 

Power Needed in Woodworking. In the factory of the Rock- 
well Manufacturing Company, a woodworking concern in Mil- 
waukee, tests were made on two machines in the company's 
plant, each of which is equipped with more than one driving 
motor. The first test was made on a 30-in. (76.2-cnO Whitney 
planer, equipped with two 5-hp. motors. Each motor consumed 
1.1 kw. driving the machine idle, the load rising to approximately 
1.15 kw. per motor when the feed was started. The spindle 
speed of the planer was 3550 r.p.m. When the planer was taking 
a ^i6-in. (1.58-cm.) cut from four pieces of hard wood 2 ft. 
(60.96 cm.) in length each motor consumed 2 kw. The spindle 
speed of the machine at that time was 3500 r.p.m. There were 
occasional momentary surges to 3 kw. on each motor, but the 
load was fairly steady at 2 kw. during the cut. When the 
planer was operating with high-speed feed, taking a ^16-in. (7.93- 
cm.) cut from a piece of maple 22 in. (55.88 em.) wide, with a 
spindle speed of 3200 r.p.m.. the motors took 6.5 kw. each, the 
load occasionally rising sharply to 10.5 kw. When this cut was 
diminished to T ± in. (6.35 cm.) with the high-speed feed the load 
was 6.5 kw.. occasionally rising sharply to 9.5 kw. for each motor 
connected. 

The other test was made on a three-drum, 66-in. (167.61-cm.) 
door sander, equipped with four motors. The 7. 5-hp. motor at- 
tached to drum No. 1 consumed 1.2 kw. driving the drum idle. 
During the sanding operation the power consumption carried 
from 2.5 kw. to a trifle over 1 kw., but it was fairly steady dur- 
ing the majority of the time, being between 3 kw. and 1 kw. 
The 7. 5-hp. motor driving drum Xo. 2 consumed 1 kw. driving the 
drum idle and required from 2 kw. to 8 kw. while operating the 
drum under load. The 7. 5-hp. motor operating drum Xo. 3 
consumed 1 kw. with the machine idle and took from 1.5 kw. to 
5 kw. during the sanding process. The 2-hp. motor which ope- 
rates the feed required 0.3 kw. for driving the feed idle and 
0.5 kw. under load. 

From this information it may be seen that it is advisable to 
consider the hardest kinds of woods which will likely be worked 
as well as the rates of feed. Of course momentary fluctuations 
in load can be handled by the overload capacity of the motor. 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 161 
ROLLING MILL DRIVE 

As most engineers know, the general problem of electric drive 
in rolling mills is now purely an economic one, the fundamental 
question being whether such a drive is or is not cheaper than a 
steam-engine drive, and, granted that it is, whether it is cheaper 
to generate or to purchase power. Large electrical supply com- 
panies are able to deliver energy on the scale demanded by roll- 
ing mills at a figure which permits competing with power locally 
generated. The great public supply plants can work on so big a 
basis and derive so much benefit from the diversity factor that 
they are in a particularly good position to sell power cheaply in 
large blocks. The average rate offered by twenty central sta- 
tions furnishing power to steels works is, according to a recent 
report on the subject, between 8 mills and 9 mills per kilowatt- 
hour. The methods of charging adopted are usually based on 
certain requirements for maximum demand plus a flat rate. 
Only in rare instances is the latter system of charging used 
alone. As is well known the arrangements adopted for equaliz- 
ing the enormously irregular loads in rolling mills are highly 
ingenious and on the whole very successful. For the present 
purposes it is sufficient to point out that the difficult problems 
presented have been very successfully solved, so that there is no 
sound reason for central stations in general being timorous about 
taking on rolling-mill load, assuming that its quantity is not so 
great as quite to swamp the station capacity. Generally, special 
provisions in the feeding system are necessary, and some extra 
care must be taken in the matter of regulation. 

Advantages of Electrified Rolling Mills. The trend of evolu- 
tion in iron and steel plants has been to electrify every machine 
up to and including the main rolls, owing to the greater flexibil- 
ity of operation and control of the electrical machine as compared 
with the steam engine, says William Knight, formerly assistant 
mechanical engineer of the Crocker- Wheeler Company. Among 
factors which must receive consideration in the electrification of 
the steel mills are the following: First of all is efficiency. 
There is no doubt that in an electrically driven rolling mill the 
cost of the power can be conveniently controlled by using the 
most suitable arrangement in the electrical plant. Furthermore, 
the elimination of the losses in the boiler room and all along a 
steam pipe line which is made possible by buying the power from 



162 ELECTRICAL AIDS TO GREATER PRODUCTION 

an outside source will still further reduce the cost of operation 
per ton rolled. The output of an electrically driven rolling mill 
is also larger than it would be with steam drive, owing to the 
rapidity with which the mill can be controlled and handled and 
the uniform torque exerted by electrical motors equipped with 
flywheels to carry them over peak loads. 

The economy of space that can be effected by buying electricity 
from an outside power station instead of installing a steam- 
power plant in the works, and the possibility of measuring very 
accurately the amount of power needed for rolling a given sec- 
tion (thus allowing a very close estimate of the manufacturing 
cost of any product), are the two points that, in these days of 
high cost of land and keen competition, speak strongly in favor 
of electric drive in rolling mills. 

It need hardly be said that in a rolling mill the demancl of 
power generally varies rapidly between wide limits. "When the 
ingot enters the rolls a large demand of power occurs, and as 
soon as it leaves the rolls the power demand may suddenly be 
reduced to that required for overcoming the friction losses in 
the mill itself and in the motor only. This rapid fluctuation of 
power which occurs during the operation of a rolling mill, if not 
corrected somehow, will create a very unfavorable condition for 
rolling at the lowest price, since this price is contingent on the 
condition that the power demand should be. as much as possible, 
maintained steadily at the full capacity of the generating plant. 
To meet this requirement, however, in some cases may mean an 
increase in capital cost and a large increase in friction losses 
which may not be offset by the saving effected by obtaining the 
power at a lower price. 

The operation of a rolling mill, like any other engineering 
problem, is a commercial proposition aiming at the largest pos- 
sible production obtained with the least expense, so that the best 
results are reached through a compromise between the advan- 
tages and the disadvantages arising from several general and 
local conditions, the maximum over-all economy being reached 
when the combined total capital charges and running expenses 
per ton rolled become a minimum. 

Steam Versus Electric Drive. Before deciding whether to 
adopt a steam engine or an electric drive for a rolling mill the 
following points must be considered: (1) capital outlay; (2) 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 163 

steady losses; (3) saving effected with electrical motors during 
reversal, in the case of reversing rolling mills; (4) power ab- 
sorbed with partial load; (5) speed of mill as affecting produc- 
tion; (6) if the power is generated within the works, what in- 
vestment or operating expense it involves, or if it is purchased 
from a public service corporation, under what conditions the 
purchase can be made. 

In many steel plants the waste gas from the blast furnace 
may be used for generating the needed power. If the surplus of 
such waste gases is large enough, there is little doubt that it will 
be cheaper to generate the power inside of the works than to buy 
it from an outside generating plant. In plants which are purely 
rolling mills, where there are no blast furnaces in operation, 
and in small plants which do not have a very large production, 
the local generation of the power would not be in the majority 
of cases a sound economical policy, as advantages are usually 
derived by means of purchasing the power from an outside 
source. 

When figures on the paper show that local generation of 
power would be cheaper than purchased power, the fact should 
be taken into account that the only object of a public service 
corporation is to sell energy and that, in order to accomplish 
this purpose, the combined efforts of a staff of specialists are used 
in the production of a reliable source of power at the lowest 
price. In a steel plant, instead, the main object is to produce 
steel, and the production of power is only a side issue which, 
generally speaking, could not be handled as efficiently and eco- 
nomically as if the power were produced by a concern estab- 
lished for that purpose only. 

The load factor of a central station supplying energy to a 
steel mill increases with the magnitude of the plant. With small 
plants, however, the load factor is larger than would be ex- 
pected, owing to the fact that the rolling is generally done in 
multi-stand mills and a larger number of passes are taken to 
produce a desired section. Also, in many mills, several pieces 
are rolled at the same time, the result being a more uniform load 
with multi-stand mills than with the large single-stand mill. 
The load factor is an important item and affects a good deal the 
cost of the power. 

How Selection of Equipment Depends on Energy Contract. 



= r 



- U - L 



•3 S 



1 '- 









5c - 



— 
< 



Z z — ' Z ? — ' - ^ £ 



x 


_= 






> 


jj 






X 


u 






- 


w 






'-=- 


r 






z 


~ 


?nox Jq5ia^\i 


IO 


~ 


^ 


:^-- • : .£ 


•a 


— 


z 






O 


1 


•dn *»nd4no 


£ 


z 


- 


JOJOft 


•C 


— 


^ 




bi 


X 








- 




rada "paadg 




X 




umaiixBj^ 


- 


z 


_ 


urd-g -aubjoj, 


c— 


< 


._ _z 


— . r. 7: : x B n 




— 


z £- 






- 


o g 


■— 1 \r -r rf "i 


c 


z 


5 ~ 


nramtxBjt 


X 

— 


c 


§ E 




a 


< 


s 


dn indjno 




— 




[Bmao^v 


- 


> 






— 


- 








> 








— 






m 


K 






s 

- 


/ 




. 


- 
— 


2 




- 


>. 


- 
- 




z 
- 


- 
a 


< 




H 


— 


'- 




z 

> 


u 



> X — 



I S 2 I S 5 ~- o - 









— 





c: 


. 


C 
O 

— ' 


X 
CI 

- 


c 
c 

--. 


CI 

--. 


c 


o 

X 


C 
X 
t-1 


o 





— I -= 



— 


— 










t- 


E 


■ 


— 
= 


= 


£ 


- 








~= 


— 


z 


- 


a 


t~ 


- 










Z z 










- 


s .~ 



- = 

- — 
= 



a 



- 

'- 



~ z 

= 

X 

_- 

— d 

! -. 

- m 



- : 1 : 



- 



- 



•- z 

- - 



- 



— 



_ ; 

= z 

. x 

= - 

- z 

_- s 

: 



Z 
- 



— 



- - 



_ - 
— > 



— 


— 


= 














- 




- 


- 


- 




- - 


- 






- 


^ 


-_ z 


- 


z 



-S — s 



- - 

z ■ 

i." - s 

- = 

- s 



164 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 165 

When energy is charged for on maximum demand the introduc- 
tion of a flywheel is necessary in order to minimize the load fluc- 
tuation and thus obtain the lowest possible rate. When a flat 
rate is offered there is no need of using an equalizer flywheel for 
reducing the cost at which the power is purchased. Instead, a 
motor large enough to take up the peak loads on the mill could 
be used, thus eliminating the bearing and windage losses of the 
flywheel. This, however, may be objectionable because of the 
large size of motor needed. A convenient compromise may be 
reached by using a comparatively small flywheel and a motor of 
a convenient size. 

In the third case, when peak loads of a long duration only are 
objected to, a motor of varying speed may be used. In merchant 
mills it is an advantage, and practically a necessity, to be able to 
vary the speed of the mill motor. The roughing rolls of a mer- 
chant mill must be run at a high speed. The finishing rolls, on 
the contrary, must be able to run at different speeds, according 
to the size and the shape of the section being rolled. 

With a direct-current power supply this is a comparatively 
simple matter, the speed variation being obtained by means of 
field regulation only. With alternating-current motors this re- 
quirement is not so easily met, and a serious loss is experienced, 
since the efficiency of alternating-current motors decreases prac- 
tically in proportion to the decrease in speed when the regulation 
is attained by the introduction of resistances in the rotor circuit. 

Assuming that the power is transmitted to the rolling mill by 
alternating current at high pressure, there is no question that 
induction motors should be used for driving the main rolls. 
There is, however, a difference of opinion as to whether the so- 
called auxiliaries should be driven by alternating-current or 
direct-current motors.' This latter point was discussed by B. R. 
Shover and E. J. Cheney in the London Electrician of Oct. 18, 
1912, where very careful estimates are published of the capital 
expenditure and working expenses under the two systems in a 
certain hypothetical case which is fairly representative of a large 
mill. The conditions under which the one system or the other 
is to be preferred and the advantages and disadvantages of both 
are fully stated. The authors conclude by stating that when the 
percentage of power required for auxiliary apparatus (exclusive 
of pumps) is 25 per cent or less of the total power delivered to 



166 ELECTRICAL AIDS TO GREATER PRODUCTION 

the mill, and where the power factor of the entire mill, includ- 
ing main and auxiliary apparatus, is more than 70 per cent, the 
alternating-current • system should be used throughout, a saving 
being thereby effected in working expenses and in the absence 
of complications. 

TABLE XXV— COMPARISON OF FIEST COSTS OF STEAM AXD 
ELECTRICALLY DRIYEX REVERSING MILLS 

(10-In. Blooming Mill Rolling 60..000 Tons of Steel a Month) 

ELECTRIC DRIVE WITH PURCHASED POWER 

Complete cost of reversing motor, flywheel motor-generator set, 

exciters and control equipment $185,000 

Foundations, wiring, etc 10,000 



Total $195,000 

ELECTRIC DRIVE WITH POWER GENERATED AT PLAXT 

Complete cost of reversing motor, flywheel motor-generator set, 

exciters and control equipment §185,000 

Foundations, wiring, etc 10,000 

Proportion of power house cost, 2500 kw., at $50 per kw 125,000 

Transmission and outside wiring 5,000 

Total $325,000 

STEAM DRIVE 

Compound reversing engine $125,000 

Condenser, exhaust piping, including pumps 25.000 

Foundations % 10,000 

Boilers, 2500 hp., including stokers and coal-and-ash-handling 

plant, at $30 per hp 75,000 

Steam piping with covering, valves, etc 15,000 

Water tunnel for condenser, with discharge for 8500 gal. of water 

per minute 50,000 

Total $300,000 

If the power is generated within the works, it is always a good 
policy to install motors which, in case a breakdown should occur 
in the generating station, could be operated from the plant of a 
local public service company, thus avoiding serious losses due to 
interruption of output. 

The action of rolling-mill motors may sometimes create a sen- 
sible fluctuation in the voltage, thus disturbing the performance 
of other machinery. To obviate this inconvenience a flywheel of 
a convenient size may be provided with a suitable arrangement 
for slip regulation which, by decreasing the speed of the motor, 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 167 

will allow the flywheel to give up enough of its stored energy to 
make up for the difference between the maximum peak load on 
the mill and the overload capacity of the motor. 

In some cases a flywheel of prohibitive size may be needed for 
this purpose, and this means large windage and bearing losses 
that are a constant burden on the cost of production. By in- 
creasing the slip of the motor more stored energy can be given 
up by the flywheel, and a smaller one could be used for the pur- 
pose. For instance, with a 10 per cent fall in speed 20 per cent 
of the energy stored up in the flywheel can be utilized, and with 
20 per cent fall in speed 36 per cent of that energy can be used. 
When 20 per cent speed variation is figured on between no load 
and double full load (which is about the maximum momentary 
overload that commercial machines can stand), it does not neces- 
sarily follow that this variation will be experienced under actual 
working conditions, because when the work at the mill is being 
carried on fairly steadily the power demand never drops to zero, 
neither does it reach double full-load value except under very 
exceptional conditions. 

Considerations Necessary in Applying Motors. 1 In many 
cases, owing to the low speed of the mill and to the high cost of a 
low-speed motor with good electrical characteristics, a high-speed 
machine is used and connected to the rolling-mill shaft by means 
of gears or ropes. When a directly coupled machine is used it is 
always desirable to use a flexible coupling in order to render less 
severe the shocks on the motor during the operation of the mill. 
With either coupled or geared motors the design of the motor 
bearings must be particularly good if serious troubles are to be 
avoided. Ropes or gear drives will allow the use of a higher- 
speed machine, which is both more efficient and less expensive. 

The most suitable place to mount the flywheel is on the highest 
speed shaft, but this arrangement imposes an extra strain on the 
gears or ropes. To avoid this the flywheel can be mounted on a 
separate shaft directly geared to the mill. As stated before, by 
using a larger slip a smaller flywheel can be used for supplying 

i In two articles published in the Electrical World on Sept. 30 and Dec. 
16, 1916, the writer suggested a simplified method for calculating the proper 
size of motor and flywheel to be used when the demand of power on the rolls 
at any moment is known. The graphical solutions given should be found 
very handy in avoiding long calculations. 



168 ELECTRICAL AIDS TO GREATER PRODUCTION 

the required amount of energy during the peak loads. However, 
there is a serious objection against this practice — the increase in 
cost of production brought about by the reduction of the output 
of the mill and the drop in the efficiency of the motor, if an 
alternating-current motor is used. 

The use of a separate motor-generator and flywheel set for 
supplying the power needed by the mill motor will obviate this 
objection. In this case a motor large enough to stand the peak- 
loads on the mill will have to be used. The motor-generator set 
can run at a considerably higher speed, and by regulating the 
field current of the generator the voltage of this machine may be 
varied, causing the speed of the mill motor to increase rapidly or 
decrease correspondingly. 

This arrangement is generally known as the Ilgner system. 
With it, owing to the high speed of the motor-generator and fly- 
wheel set, a comparatively small flywheel may be used, and, al- 
though the loss of power taking place in the electrical machines 
is increased, the speed of the mill can be varied at any moment 
by any desired amount. The increased output of the mill will 
more than compensate for the increase in losses and the consid- 
erable increase of capital cost of the electric plant. An addi- 
tional advantage with the Ilgner system is that any mill can be 
used as a reversing mill. 

Particulars x of several successful electrifications of steam- 
driven, non-reversing rolling mills, together with data on power 
consumption for rolling different classes of materials, follow: 

TABLE XXVI— STATISTICS OF MOTOR DRIVEN MILLS i 

Hamilton, Bethlehem, Massillon, 
Ont. Pa. Ohio 

Size of ingot, in 15x17 19 x 23 18 x 20 

Weight (lb.) 4,000 10,000 5,000 

Size of finished material (in.) 4x4 4x4 4x4 

Elongation 1G 10-12 Up to 20 

Number of passes . 19 17-21 19-21 

Capacity (tons per hour) 00 100 60 

Roll diameter (in.) 30 30 30 

i Obtained from a paper by W. F. Mylan read before the British Institu- 
tion of Electrical Engineers and from another paper by Koettgen and Ab- 
lett before the Iron and Steel Institute. 

i From paper presented before June 1916 meeting of A. I. E. E. by W. 
Sykes and D. Hall. 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 169 

Hamilton, Bethlehem, Massillon, 

Ont. Pa. Ohio 

Pinion diameter (in.) 34 35 34 

Speed, full motor field (r.p.m.) 70 40 50 

Speed weakened motor field (r.p.m) . . 100 120 120 

How driven from motor Direct Direct Direct 

Number of motors 2 2 1 

Voltage across each armature 600 600 700 

Maximum operating torque (ft.-lb) . . 900,000 1,550,000 750,000 

Maximum motor horsepower 10,000 12,000 8,000 

Number of generators 2 2 1 

Rated hp. of driving motor of set. . . . 1,800 2,000 1,500 

kw. 

Weight of flywheel (lb.) 100,000 100,000 60,000 

Speed of flywheel motor-generator set 

(r.p.m.) 500 375 375 



Cold Rolling-Brass Merchant Mill. — This mill consists of one 
set of breaking-down rolls, one set of second breaking-down 
rolls and two sets of finishing rolls. The breaking-down rolls 
are 20 in. (50 cm.) in diameter, 30 in. (76 cm.) long, and all 
are driven at 6 r.p.m. by a long train of gear wheels. Origin- 
ally this mill was driven by a single-cylinder horizontal non- 
condensing engine 28 in. (71 cm.) in diameter, 48 in. (122-cm.) 
stroke, and run with a boiler pressure between 60 lb. and 80 lb. 
per square inch (4.2 kg. and 5.6 kg. per sq. cm.). The usual 
size of ingots dealt with in this mill is 3 in. by 1^2 in. by 7 ft. 
(7.6 cm. by 3.8 cm. by 2.1 m.) rolled down to various gages. 

The motor used now is a 200-hp., 240-r.p.m., three-phase slip- 
ring motor, direct-geared by means of cast-iron gear to the mill. 
The gear ratio is about 4.8 to. 1. No flywheel is provided. 
This equipment has proved extremely satisfactory, and a con- 
siderable reduction in the cost of operation and increase in the 
output has been obtained. 

Iron and Steel Merchant M ill. — The mill consists of five pairs 
of 12-in. (30.6-cm.) rolls running at a minimum speed of 80 
r.p.m. and is driven through double helical steel gears (ratio 1 
to 2.5) by a 200-hp. direct-current motor at from 200 to 450 
r.p.m. Since the mill was electrified an increase of output of 
over 30 per cent and decrease in the power consumed of 60 per 
cent have been obtained. 

Power Consumption for Rolling Different Classes of Mate- 
rials. Re-rolling 90-lb. (45 kg. per m.) rails to a section 16 lb. 



170 ELECTRICAL AIDS TO GREATER PRODUCTION 

(8 kg. per ra.) per yard, each piece 30 ft. (9.1 in.) long, re- 
quired 56 units of energy per ton. Total output of mill, 4800 
pieces per twelve hours. Small mining rails were rolled from 
billets 5 in. by 53 4 in. (12.7 cm. to 14.7 cm.), weighing a maxi- 
mum of 900 lb. (408.2 kg.). In the case of 28 lb. per yard (14 
kg. per m.] this comes to an average of 650 lb. (291.8 kg.) ; in 
the case of 18 lb. (9 kg. per m.) rails the requirement is as 
follows per ton rolled: 28 lb. (11 kg. per in.), 38 units; 21 lb. 
(12 kg. per m.), 12 units; 20 lb. (10 kg. per in.),. 15 units; 18 
lb. (9 kg. per in.), 48 units. Smaller rails of 12-lb. and 8-lb. 
(6 kg. and 1 kg. per m.) section required from 19 to 51 units 
per ton rolled. 

Girders 11 in. by 6 in. (27.9 cm. by 15.2 cm.) can be rolled 
for about 50 units per ton. Channels averaging IV2 in- by % 
in. by 2 in. (3.8 cm. by 1.9 cm. by 5.09 cm.) require 66 units. 
Angles 3 1 /2 in. by 3% in. by % in. (9.5 cm. by 9.5 cm. by 1.6 cm.) 
from 800-lb. (362.9-kg.) billets require 50 units. Sheet (iron) 
8 ft. 3 in. by 33 in. by 0.061 in. (2.5 m. by 8A cm. by 0.16 cm.) 
require 95 units per ton; sheet (iron) 8 ft. by 18 in. by 0.08 in. 
(2.1 m. by 1.2 m. by 0.21 cm.), 70 units per ton; sheet (iron) 
10 ft, by 18 in. by 0.067 in. (32.8 m. by 1.2 m. by 0.17 cm.), 80 
units per ton; sheet (iron) 10 ft. by 18 in. by 0.125 in. (32.8 m. 
by 1.2 m. by 0.32 cm.), 60 units per ton; sheet (iron) 9.5 ft. 
by 12 in. by 0.09 in. (2.81 m. by 1.07 m. by 0.21 cm.), 81 units 
per ton, from billets of 7.9-in. by 7.9-in. (20-cm. by 20-cm.) 
section, weigh 388 lb. (175.9 kg.). 

MOTORS IN THE TEXTILE INDUSTRY 

There has been a rapidly increasing use of motors in textile 
mills, an art which dates back verv nearlv five-and-twentv vears, 
but which has been rapidly improved as conditions have grad- 
ually led to the adoption of more and more independent methods 
of motor driving. In the beginning the cotton industry clus- 
tered about water powers where motive power could be cheaply 
obtained. As the steam engine became more highly developed 
in efficiency and as mills outgrew their normal supply of water 
power and fell back upon steam auxiliaries, the waterwheel 
found relatively less and less use. In the forty years from 
1870 to 1910 it had fallen from 60 per cent of the total to about 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 171 

20 per cent. Steam power had increased from some 40 per cent 
to 60 per cent, and the remaining 20 per cent was furnished by 
electric power. It has been estimjated that by 1920 the per- 
centage of electric power will easily have doubled. In the earli- 
est electrical mill drives the steam engines were replaced by 
fairly large motors employed for group driving. The steady 
tendency of late years has been more and more toward individ- 
ual drive, which is easily employed in new mills and gives 
greater possibilities of power economy than have been afforded 
by the methods that it supersedes. 

Probably the typical mill consists of a combination group and 
individual drive, the former for certain machinery operated, so 
to speak, in blocks, each consuming no very great amount of 
power in the aggregate ; the latter for the heavier and more inde- 
pendent work. For mill work the induction motor is chiefly 
used, since for most classes of work unusual flexibility of speed 
regulation is not required. At the beginning of the art com- 
petition with direct-current machinery caused the building of 
induction motors with extraordinarily low speed variation, a 
tendency which has of late given way to more normal design. 
In a few places in mills motors of special type have to be em- 
ployed on account of the presence of large amounts of dust and 
lint in the air, and in some cases because of troublesome vapors 
that arise. 

Experience shows that the electric drive for this work has not 
only the usual advantages of facilitating a cheap supply of 
motive power but also leads to a larger and more uniform output 
on account of the better operating characteristics of subdivided 
motive power. There is every indication that the use of motor 
drive in mills is going to increase steadily, bringing the greater 
water powers into active use in this class of manufacturing and 
superseding not a few of the steam drives now in use. 

Loom-Motor Switches. In weave sheds where hundreds of 
looms are in service and tended by young girls with no electrical 
or mechanical training, simplicity of control, combined with 
entire safety of operation of operation, is of vital importance, 
particularly where the motors are wound for 220 volts and up- 
ward. In one installation the looms are mounted with ends 
reversed, and the adjacent motors are thus brought within 2 
in. or 3 in. (5 cm. or 7.6 cm.) of each other. Near the floor in 



172 ELECTRICAL AIDS TO GREATER PRODUCTION 

the intervening space is mounted a single fuse box and two 
heavy-duty snap switches serving the two loom motors. 

Each switch is of the most rugged type, capable of withstand- 
ing much abuse. The handles are recessed in disks marked for 
"off" and "on" positions, and short connections are run to the 
motors with BX conduit. Nothing short of deliberate destruc- 
tion is likely to affect the operation of these units. It is feasi- 
ble by staggering the loom motors with respect to the interme- 
diate aisle to provide for a quicker inspection than would be 

ssible with a purely symmetrical arrangement. The space 
between loom ends is of insufficient value to justify reserving it 
for the passage of the operator or inspector, and the economy 
in wiring secured by double switch mounting close to the loom 
motors is considerable in a large installation. 

ELECTRIC DRIVE IN THE PRINTING TRADE 

Much of the electrical development work done in the printing 
trade is quite comparable to that in other branches of manufac- 
ture and involves nothing unusual in the way of motor equip- 
ment save ordinary care in the adaptation of individual drives. 
The presses require the closest attention to obtain successful 
results, and the problem in this case is quite like that encoun- 
tered in the paper-making machine, where there is likewise ne- 
cessity for good speed regulation, for heavy starting torque to 
overcome the inertia, and for inching the machinery along very 
gradually during certain stages of the operations. It is not 
unusual in large presses, indeed, to apply the same two-motor 
device as in the calenders, a small machine being used for the 
very slow movement, a big one for the regular running. 

Barring starting torque, the power required by printing 
presses is rather surprisingly small. The press-driving problem 
is essentially one of varying speed, and the means adopted for 
this purpose are substantially those used elsewhere, of varying 
the field and resistance in the armature circuit enough in each 
case to give the required range of speed. The interpole motor 
lends itself particularly well to such control here as in other 
cases. "Where alternating current has to be used one is gener- 
ally driven to slip-ring motors with variable resistance. As the 
running load of a press is fairly uniform, this arrangement can 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 173 

be made to work successfully despite the fact that, as in series- 
wound continuous-current motors, the speed varies through a 
certain range with changes of load. The control adopted is gen- 
erally of the push-button type and frequently from several 
points, the form and multiplicity of control being chosen for 
safety and convenience. 

It is in the adaptation of this type of control to the require- 
ments of the particular printing plant considered that the 
greatest ingenuity can be exercised by the engineer. Aside 
from this, the equipment of printing machinery is a very simple 
matter. 

POWER REQUIREMENTS OF TRAVELING CRANES 

The electric crane has become practically standard for all 
permanent work and for much temporary work. As its use has 
become more familiar the motor drive has been more and more 
refined. The things most imperative in its organization are un- 
usual mechanical strength, accurate speed control and reliability. 
These have led to the development of many highly specialized 
devices and have resulted in apparatus which has proved ex- 
ceedingly successful from every standpoint. One particular 
point in design to which attention should be directed is the 
question of efficient co-ordination between the speed and the 
requirements of the particular work for which the crane is 
designed. Here more than anywhere else is the finesse of the 
engineer needed in planning a successful crane equipment. 

FACTORS THAT GOVERN ELEVATOR DRIVE 

The electric elevator has been coming into its own within the 
last decade at a very surprising rate. As the demands of ele- 
vator service have increased both in speed and in lifting power, 
it was only natural to fall back on the general source of distrib- 
uted energy for means of operation. The electric elevator is 
economical in operation, easy to keep up, simple and compact, 
and safety devices may be applied to it with the extreme facility 
which characterize most electrical modes of driving. 

The principles of the design of the lifting gear are pretty 
much the same for all sorts of motive power. For most practi- 



174 ELECTRICAL AIDS TO GREATER PRODUCTION 

cal cases the winding drum or the traction sheave in some form 
or other is used, the latter more generally. So far as the motors 
themselves are concerned, the requirements are somewhat spe- 
cial, chiefly in the direction of high starting torque, and in 
direct-current machines sparkless operation even under extreme 
variation of load and overload. It is also rather necessary that 
the operation should be quiet, unless of course in freight service 
in buildings otherwise far from noiseless. The result has been 
the development of a somewhat highly specialized class of 
motors, generally now-a-days with commutating poles, designed 
for high overload capacity and with large mechanical factors of 
safety. 

BLOWER AND COMPRESSOR SERVICE 

The power requirements of fans and other devices for pro- 
ducing movement of air vary enormously with the requirements 
to be met. Ordinary fans of the type familiar to every one 
have for their special function the movement of a large bulk 
of air at relatively very low pressure. For moderate pressure 
blowers of the familiar centrifugal type are commonly used, 
and for high pressures the two-stage or three-stage units built 
along the general lines of the reciprocating steam engine. All 
such apparatus has one common characteristic in that the power 
required varies rapidly with the speed, practically as the cube 
of the speed for a given area of discharge opening. Conse- 
quently the starting torque is very slight, which separates 
blower service from almost every other variety of motor drive. 
The efficiency of the apparatus does not vary to any material 
extent with variations in speed, again an almost unique charac- 
teristic. The light starting torque greatly simplifies the equip- 
ment of motors and lessens the severity of their sudden require- 
ment for power at the moment of starting. 

Almost any sort of motor is, therefore, suitable for blower 
service. Single-phase alternating-current motors, often looked 
at askance on account of their low torque at starting, serve 
admirably in operating fans and blowers. Induction motors of 
the simplest kind are entirely adequate for this service. When 
the supply is direct-current either shunt or series motors may 
be used, the former being generally preferable. The control of 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 175 

fan and blower motors is obviously a very simple matter, the 
smaller sizes requiring nothing more than a connecting switch. 
Large machines should have at least a starting rheostat and now 
and then under exceptional conditions an overload release. 
Only in high-duty compressors is there special call for any elab- 
oration of the starting equipment, such as is common with other 
motors. As the speeds required for rotating blowers of every 
sort are rather high, direct connection of the motor is very often 
practicable, although the best speed of fan may not agree well 
with the quasi-synchronous speeds of alternating-current motors. 
Large blowers should generally be planned for direct connec- 
tion, while belting is very often convenient in the smaller sizes. 
It is perfectly practicable to use either method, and either can 
be made silent, an important characteristic in much ventilating 
work. Belted machines have some advantage in this respect 
when the fan speed is relatively low. It takes a good deal of 
finesse on the part of the designer to secure a silent fan of re- 
spectably large output and advantageous speed, but the trick 
can be turned successfully. 

IMPROVING MOTOR DRIVE IN MAINE SHOE 

FACTORY 

Several improved motor applications are used in the Lunn & 
Sweet shoe factory, Auburn, Me. In the stitching-room eight 
"Peerless" fold cementers were formerly belted to a 3-hp. motor 
which also ran twelve sewing machines. At present four ce- 
menters are mounted on a single bench, constituting a produc- 
tive unit, each machine being directly belted to a 0.1-hp., 110- 
volt General Electric (Fort Wayne) induction-type motor. The 
eight cementers require but 0.8 hp. when all are in service, and 
these motors are more efficiently loaded than under the previous 
arrangement. A separate snap switch at each operator's posi- 
tion controls the motor, thereby affording maximum ease of 
control and saving energy. 

A number of sewing machines were formerly driven in large 
groups by motors ranging in size from 1.5 hp. to 5 hp. This 
service has now been subdivided so that in a typical case five 
sewing machines are grouped on a 1-hp., two-phase, three-wire, 
440-volt induction motor. In the older arrangement, which in- 



176 ELECTRICAL AIDS TO GREATER PRODUCTION 

eluded more machines and larger driving units, control was 
effected by a four-pole fused switch mounted on walls or posts. 

Subdivision has enabled a more compact switch to be utilized. 
The fuses are enclosed in a fireproof box under the table, and 
the motor switch is a three-pole snap-type unit of General Elec- 
tric make, used largely in the latest individual textile-drive in- 
stallations. Entire satisfaction has resulted from the use of 
these snap switches on 4-AO-volt power circuits at this factory. 
The former motor arrangement was less convenient, the motors 
being mounted in perforated metal boxes on top of the benches. 
Here three 2-hp., 440-volt, two-phase motors operated twenty- 
six Singer sewing machines, the starting switches and fuses being 
placed on the back of the bench in each case. 

Probably a 5-hp. motor is the most convenient size used in an 
ordinary shoe factory, on account of the convenience with which 
this size may be utilized either singly or in combination drives. 
Thus, a pair of such motors are belted to a line shaft from which 
are operated nine rotary shoe pounders. Special care in deter- 
mining the proper pulley sizes enables this service to be handled 
between two units, each taking half the load. The two motors 
in this case are two-phase, four-wire machines and are protected 
by one fuse in one wire of each phase, or two fuses per motor. 

ADVANTAGES AND METHOD OF INTERLOCKING 

MOTORS 

In a great many manufacturing operations it is frequently 
found that a machine may require more than one motor in order 
that the different operations of the machine may be changed 
with respect to other operations of the same mechanism. This 
is true particularly with cutting machinery, where the rate of 
material feed should be adjustable in order to handle various 
sizes of stock. As examples of machinery in which this charac- 
teristic is necessary, planers, wood saws, diamond marble saws, 
sizers and other tools in which the cutting is practically constant 
but the feed variable may be mentioned. 

As long as the cutting motor and the motor operating the 
variable feed are both running, the entire machine operates 
satisfactorily, but should the cutting motor blow a fuse, trip its 
relay or be stopped by the operator and the feeding motor con- 






MOTORS, CONTROL, SPECIFIC APPLICATIONS 177 

tinue to run, serious trouble is liable to follow. The feed will 
force material against the powerless cutters and either bend or 
break parts of the equipment. Most feeds operate rather slowly 
by being geared down many times from the motor shaft, so that 
the feed motor, though very small, may have enormous power 
on the slow-moving rolls or carriage handling the material. 

Trouble can be obviated easily on any machine operating 
under power from two or more motors, David R. Shearer points 
out, by interlocking the no-voltage-release coils on the starters or 
compensators. The illustration in Fig. 62 indicates a driv- 
ing and a feed motor operating in an interlocking manner on 
three-phase alternating current. It will be noticed that current 

Overload Relay Contact^. 

I . -L i\ 



No Voltage 
'- Release 



COMPENSATORS 



No Voltage 
c Release 



Fig. 62 — Method of Interlocking Two Motors Through Their 

Compensators 



is taken from the driving motor leads through both release coils 
and both relay trips on the two compensators. Thus, if the cut- 
ting or drive motor is stopped or fails, the current is broken in 
the release coil of the other machine and it stops also. More- 
over, if either motor becomes overloaded sufficiently to trip the 
relays the entire set is at once brought to a stop. 

By the addition of a double-throw switch the coil-operating 
current may be taken from the leads of either motor as desired. 
This is sometimes advisable when it is necessary to operate one 
of the motors singly for some specific purpose. This method of 
interlocking may be extended to cover several motors operating 
interdependent mechanism, and the actual arrangement of con- 
nections may be subject to many changes; but the principle 
remains the same. 



178 ELECTRICAL AIDS TO GREATER PRODUCTION 

METHOD OF PREVENTING CONCURRENT PEAKS 

Sometimes a manufacturing plant will be found in which the 
connected motor load is greatly in excess of the plant generating 
capacity. When such a condition exists there is a possibility 
that the machinery may be subject to a concurrent peak which 
will mitigate against normal production. For instance, the volt- 
age may drop to a point where the low-voltage releases trip out, 
thus stopping all the motors and introducing serious delays. 

A case of this kind was called to D. R. Shearer's attention 
some time ago in a woodworking plant where it was exceedingly 
difficult to get the operators to understand the seriousness of 
allowing a peak to occur on several machines at the same time. 
Such a condition actually occurred once or twice each day. 
Each time this happened the manufacturer lost several dollars, 
so it was determined if possible to obviate the trouble. The 
blame could never be placed on any one man, and thus it was 
not feasible to get the desired result through discipline. 

The trouble was corrected by placing a large ammeter in plain 
view of the operators of three of the largest machines. On the 
ammeter dial, which was printed in large figures and well illumi- 
nated, was placed a danger mark, and the operators were in- 
structed never to allow the load to run the pointer above this 
mark. Since the entire motor load was indicated on this instru- 
ment, it was not subject to violent fluctuations, but remained 
very steady until several machines began to take heavy cuts at 
the same time, when the pointer gradually moved up toward the 
danger mark. 

There was some fear that the use of this ammeter would cur- 
tail production, but this proved not to be the case. In fact, the 
production was increased, for not only were delays from over- 
loads obviated but the load factor was improved. This is ex- 
plained by the fact that the men could see when the load was 
dropping and so could increase the feeding proportionately. 

It is possible that the use of an ammeter might be of consid- 
erable benefit even in those plants having abundant power by 
tending to better the load factor and consequently the produc- 
tion of all the machines. If a minimum point as well as a 
maximum were indicated on the dial and the entire plant load 
indicated on the meter, it would appear that great gains in 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 179 

economy might be expected with attendant increase of produc- 
tion, simply from the efforts of all the operators to keep the 
needle in its restricted space on the scale. 

METHODS THAT FACILITATE PROMPT 
MAINTENANCE 

Card Record System. In a large plant where more than 100 
motors are installed much delay was experienced in answering 
breakdown calls and in making repairs through lack of knowl- 
edge of each particular motor. One of the first things done by 
the new chief electrician, says H. S. Rich, was to have all motors 
cleaned up and numbered plainly. Then he established a card 
system on which were kept all the specifications concerning each 
motor. These cards were kept in an open box on his desk in 
the electric repair shop, where all the helpers could refer to them 
instantly. Each card showed the following: 

Number of motor. Department. 

Horsepower. Revolutions. 

Make. Phase. 

Manufacturer's number. Diameter of pulley. 

Face of pulley. Diameter of shaft. 

Length of shaft. Size of key. 

Type. Serial number 

Size of fuses. Type of fuses. 

Size and number of brushes. Motor belted to. 

The cards were arranged in the box by departments so that 
by referring to any one department all the motors in there could 
be seen at a glance. A few cards at the front of the pile had 
all the motors in the plant arranged by numbers consecutively, 
so that when any foreman telephoned in, for instance, that 
motor No. 15 was stopped the top cards showed what depart- 
ment this motor was in. Then by referring to the department 
card all the specifications concerning this motor were seen at a 
glance, and the repair man was supplied with the proper-sized 
fuses, test lamp and tools and dispatched to remedy the trouble. 

Most jobs were completed in record time because the necessary 
things were taken along on the first trip, without running back 
and forth to see what was wanted, all of which formerly caused 



180 ELECTRICAL AIDS TO GREATER PRODUCTION 

much delay. By "keeping tabs" on the cards all sizes of fuses 
likely to be needed by any motor could be provided ahead of 
time and kept in stock, so that no time was lost making up any 
when a motor shut down. 

This card system was very handy to refer to when a motor 
burned out or broke down. Moreover, motors could be shifted 
around to better advantage by knowing all about them. Thus 
one department needed more horsepower and another depart- 
ment was found to have a larger motor at the same speed and 
pulley diameter. After seeing them both in operation an ex- 
change was made with all knowledge of the details before either 
was stopped. Many times an exchange or temporary installa- 
tion called for special-sized pulley with a particular bore and 
key. The card data made possible the assembly of this material 
ahead of time so that when the change was made there was no 
loss of time. 

All new motors purchased, whether put into immediate use or 
into stock as reserves, had their record taken and listed along 
with the rest of the equipment on hand. In a space at the bot- 
tom of every motor card remarks were often penciled from time 
to time as trouble was found. Thus one busy 50-hp. motor was 
found to have very little clearance under the rotor when tested 
with a steel gage. This was noted on its card, and two new 
bearing linings were immediately made ready. On the first 
Saturday afternoon following, when the motor was shut down, 
the linings were examined and one was found to be badly worn. 
A new one was put in, and on Monday morning everything was 
ready for service with no loss of time. 

Sometimes higher line-shaft speed was demanded, and by re- 
ferring to the card the revolutions, pulley diameter, face and 
key were observed at a glance. A larger one could be made 
ready and slipped on the same day at noon ; whereas to climb a 
ladder and take measures might have meant to shut down a 
motor which was carrying a large load ; thus production would 
be curtailed. The time saved is the most valuable feature of 
this scheme. 

When summer repairs are made each motor is taken in its 
turn and thoroughly overhauled. By following the cards none 
is overlooked. Also by listing the various sizes of shafts 
throughout the plant enough bearing linings can be ordered 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 181 

ahead of time and kept in stock so that no motor will be held 
up in an emergency for lack of them. 

Motor-Data Sheet. To avoid the usual lack of complete data 
bearing upon motor applications in industrial plants, a Massa- 



For . 

Dept. 



.Bldg. 



MOTOR 

Date i?i 

Sect Floor Size B.P 



Voltage - 230 D. Duplicate of Shunt 

Similar to Drive on Uaen.Ho.... ...Compound Wound 

Series 



Constant 
Variable Speed 



Hormal Speed. 



■By Armature. 
.By Field.... 



Direct 

Clutch Connected. Back Geared.. Ratio.......... Reversible. 



Pulley Diam ....Face... tv .... 

Arranged for Floor Mounting 

Ceiling Suspension 

Make Recommended by Drafting Dept. 

Catalogue •„ 



,. Teeth in Gear Sliding Kail Base. 



Enclosing Covers 
Mesh Enclosed 



.Type. 



.Page. 



..Plain heavy Duty Starter with Renewable Segments 

Araature- -Controller with Renewable Segments - Fan Duty. 

Compound Controlled With Renewable Segments - -Machine Duty 

Starting Resistance and Field Control with Renewable Segments. 

Overload Release 

Printing Press Type 

Self Starter - Lock and Key 

Panel with Knife Switch and Fuses 
Circuit Breaker 



Reverse Switch Dynamic Brake. 



.Single 

.Double Push Button Stations 



Number* Steps Armature 
Field. . . . 



Ship to. 



Wanted • ■ .Appropriation received. 

Ordered. From. > 

Remarks: 



Our Number. 



Fig. 63 — Combined Motor Order and Data Sheet for Use in 
Industrial Plant 

chusetts factory uses the form reproduced herewith. On a sheet 
8y 2 in. by 10% in. (21.5 cm. by 27.3 cm.) in size all the more 
essential data are listed, including the factory section, depart- 
ment and floor on which the motor is going, speed, pulley and 






182 ELECTRICAL AIDS TO GREATER PRODUCTION 

suspension or mounting details, type of covers, make recom- 
mended by drafting department, type of controller and shipping 
directions. 

On the original order it has not been customary to fill in more 
than the necessary information for the motor maker and control 
manufacturer, but the complete information desired by the plant 
is kept on the filed sheet, which is convenient in its provisions 
for all the important facts. 

Fuse Rack. To facilitate restoration of service when an in- 
terruption occurs in the shoe factory of Lunn & Sweet, Auburn, 
Me., fuses are kept in a rack built of three pairs of slotted up- 
right wooden bars of 1.5-in. by %-in. (3.8-cm. by 0.96-cm.) 
stock. Each pair corresponds to a certain numbered section of 
the factory and carries the fuse sizes normally used on the motor 
circuits of that section. In case of a report of service interrup- 
tion the maintenance man, who is informed of the factory sec- 
tion involved, seizes the fuses corresponding to that section with- 
out any loss of time, and upon arriving at the scene of trouble 
effects a replacement in minimum time. Even fifteen seconds 
saved in the restoration of service in a factory where intensive 
production is the practice counts in these days. 

Rapid cooling of a burned-out motor, with consequent in- 
creased speed of replacement, is accomplished by the use of a 
Pyrene fire extinguisher, one of which is always kept at the 
front of the cabinet. 

Map of Motor Layout. To facilitate layout and maintenance 
work, a series of roller plans has been prepared showing the 
location of every machine, shaft line, column, hanger and motor 
in the plant. The plans are drawn to a scale of % in. to 1 ft. 
(10.4 mm.-l m.) and kept in the office of the superintendent 
of buildings and maintenance, who has charge of all electrical 
service. Experience shows that a scale of 14 in. per ft. (20.8 
mm.-lm.) is preferable for future work of this kind. The plan 
is about 5 ft. (1.5 m.) long and saves many measurements in the 
field. The larger scale, however, is more convenient for all- 
around service. Such a plan can often be supplemented to ad- 
vantage by a layout of distribution circuits with the sizes of the 
conductors indicated. This can be utilized in adjusting motors 
to circuits or vice versa. 

Ernest Bragdon is the superintendent of buildings and main- 
tenance. 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 183 

SOME MOTOR TROUBLES AND HOW TO CORRECT 

THEM 

Methods of Making Temporary Motor Repairs. While most 
large industrial plants carry spare motors for use in place of 
those that are burned out, many small plants do not always have 
spare units on hand, and even when they have it frequently 
takes a long* time to install them. Since only a few coils rather 
than the entire motor usually burn out when a motor "breaks 
down," the machine can be kept running in many cases until 
it is convenient to make permanent repairs by cutting out the 
defective coils. Several methods of doing so are related by H. 
L. Hayes. 

With small-size, low-voltage motors, which usually have single 
or two-circuit Y or delta windings, this does not involve much 
difficulty. Unbalanced current may be drawn from the line 
when coils are cut out, but as a rule this will not seriously affect 
the power system. It is simply a case of whether the motor can 
carry its load and whether the winding can stand the increased 
current. If the motor is not too heavily loaded, it is possible to 
cut out quite a large number of coils and still operate the motor. 
If a motor has a large number of coils, with only a few turns per 
coil, several coils per phase can be cut out, but in motors having 
comparatively few coils, with a large number of turns per coil, 
this cannot always be done. 

Complications may arise when attempting to apply this emer- 
gency repair scheme to large motors which usually have multi- 
ple-circuit windings because cutting out a coil causes local cur- 
rents. In such a case if coils are cut out of one circuit it is 
sometimes necessary to cut out coils in all circuits which are in 
parallel with this particular phase. While this change may 
leave the phases unbalanced with relation to each other, the indi- 
vidual circuits of the phases will be equal. For instance, con- 
sider Fig. 64, in which is shown a three-circuit Y winding with 
coils cut out of A-l and C-l circuits in phases A and C. In a 
winding like this, circuit A-l and C-l may be completely cut 
out, leaving only two circuits for these two phases, but this 
would reduce the capacity of the motor a great deal. If, how- 
ever, an equal number of coils were cut out of the parallel cir- 
cuits, the motor may carry practically its entire rated load. 



184 ELECTRICAL AIDS TO GREATER PRODUCTION 

The changing of the arrangement of connections, such as con- 
verting a two-circuit Y connection into a single-current delta 
type, may also often permit emergency operation. The differ- 
ent schemes outlined reduce the capacity of the motor, but if it 
is carrying a variable load, which is often the case, continued 
operation may be maintained because even though the winding 
will heat up on the peaks, it can cool down during the light-load 
periods. 

Different applications of these principles have been made in 
a New England paper mill, where 25-cycle, 440-volt, three-phase 
motors are used and shutdown of one motor often means a large 
loss of production. Prior to cutting out coils or changing con- 



M 








A r§ 



<&# 



f3> 



W 










C 

Figs. 64 and 65 — Method of Repairing Three-circuit Y Winding and 
Two-circuit Delta Winding 

nections, tests are made to detect open circuits, grounds or short- 
circuits between phases. This is done with an ordinary lamp 
extension having one wire open-circuited and connected with a 
110-volt circuit. Although 110 volts can be used to indicate 
dead grounds or short circuits, and is relatively easy to handle, 
it is better to use the full motor voltage with a bank of lamps 
in series to make the final tests, because it frequently happens 
that 110 volts will not detect partial defects that the higher 
voltage will bring out. 

With a motor having a single-circuit winding it is a simple 
process to disconnect the separate phases, but with multiple con- 
nections this is liable to involve considerable work. It is there- 
fore much quicker to try operating the motor before disconnect- 
ing any leads, noting as nearly as possible where it flashes. The 
particular section which appears defective may then be discon- 
nected and tested for faulty coils. The objection to this method 






MOTORS, CONTROL, SPECIFIC APPLICATIONS 185 

is that more coils are liable to be damaged with every flash, but 
if time available for repair is limited such procedure permits a 
saving of several hours. Furthermore, small fuses can be con- 
nected into the circuit for the purpose of limiting the short- 
circuit current. 

Following are a few examples of how motors have been kept 
running which would ordinarily have had to be taken out of 
service for rewinding. A 50-hp. motor having a two-circuit 
delta winding broke down, spoiling a number of coils. On ex- 
amination it was found, as shown in Fig. 65, that no coils in 
phase C were damaged. However, circuit B-l of phase B was 
badly burned, so that it could not be left in circuit. A few of 
its undamaged coils were connected with parts of circuit B-2 to 



B 




/St): 






Figs. 06 and G7 — Burnt-out Double- circuit Y Winding Reconnected 
Into Single-circuit Delta Winding 



take the place of coils burned out in the latter, thus making 
nearly a complete single circuit for this phase. As several coils 
in the A-2 circuit and only one coil in A-l circuit were damaged, 
enough coils were cut out of A-l to even it up with A-2. This 
motor would not have carried a heavy continuous load, but it 
was used for over two months during the cold weather to run a 
circular saw. 

Another 50-hp. motor having a two-circuit winding broke 
down, injuring only two coils. With only these two coils cut 
out the winding heated up in a few minutes, though running 
light. The coils in this motor had an exceptionally large num- 
ber of turns per coil and comparatively few coils per phase. 
Instead of trying this motor with coils cut out of other circuits, 
it was changed into a single- circuit delta winding. Thus 
changed, the motor was incapable of developing its rated power, 
but it did not have to carry a continuous load. The original 



186 ELECTRICAL AIDS TO GREATER PRODUCTION 

and final connections with coils cut out are shown in Pigs. 66 
and 67. 

In another case a motor with single-circuit Y windings, run- 
ning a small pump, broke down, injuring one coil in one leg and 
several coils in another. Cutting out the injured coils per- 
mitted more than full-load current in one phase even with the 
motor running light. Ordinarily a small motor can easily be 
replaced, but there was no spare motor available at this time. 
Since this motor could handle the load when it was running 
single-phase, a switch was connected in series with the weak 
phase to permit starting three-phase. After the motor was up 
to speed the switch was opened and the motor left running 
single-phase. The final connections are shown in Fig. 68. 




Fig. 68 — Damaged Y Winding Connected for Three-phase Starting Bui 

Single-phase Operation 

Rotors cause comparatively little trouble, but one case oc- 
curred at this paper mill where a coil-wound rotor rubbed on 
the stator and injured a number of coils. The bars which 
formed the coils in this winding had been bent after they were 
put into the slots, so it was impracticable to take them out for 
retaping. Since no new bars were available, the bad bars were 
disconnected and replaced by ordinary wire cables passed 
through the arms of the spider instead of through the slots. 

The cases mentioned illustrate that a motor is not necessarily 
"down and out" because it "shoots fire." While it is surpris- 
ing how badly a motor may be damaged and yet be capable of 
carrying its load, it is not advisable to run motors in such con- 
dition any longer than necessary, as there is a loss of efficiency 
in both motor and line. 

Reversed Phase Causes Subnormal Motor Speed. While 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 187 

working in a power plant in a small "Western town M. M. Clem- 
ent had to reconnect a three-phase, four-pole, series star-con- 
nected motor so it would operate at a different voltage. Changes 
were made according to blueprints, but when the motor was 
tested it operated at only about one-third normal speed. 

To locate the trouble the star connection was opened and oppo- 
site ends of each phase were joined to the terminals of a storage 
battery. By testing the poles of the armature with a small 
pocket compass while current was flowing in this manner it was 
found that the poles of each phase were symmetrically placed 
around the armature and that they were alternately marked 
"south," "north," etc., just as they should have been. 

Next the star connection was joined again and current allowed 





Figs. 69 and 70 — Connections and Polaeites as They Should Have 
Been in Motor Which Was Eewound 



to flow in two leads and out the third. Under this condition 
and with a properly connected three-phase, four-pole motor the 
polarity of three consecutive poles should be in one direction 
(Fig. 70), while that of the next three should be opposite, etc., 
thereby forming four flights of alternately different polarities. 
In this motor, however, it was found that the adjacent pole 
faces had opposite polarities, indicating that one phase was 
reversed. 

To determine which was reversed all of the leads were con- 
nected with the positive terminal of the storage battery, while 
the star connection was joined with the negative terminal. 
Under these conditions in a properly connected armature the 
polarities of adjacent poles should be opposite, but in this motor 



188 ELECTRICAL AIDS TO GREATER PRODUCTION 

three consecutive poles had similar polarities, while the next 
three had the opposite polarity, etc. Since the only polarities 
that could be reversed to bring about the proper arrangement 
were those corresponding to phase B, it indicated that this 
phase had been reversed ; that is, the terminal which should 
have been a lead was connected to the star point and vice versa. 

Motor Bearings Should Receive More Attention. It is to be 
regretted that electric motor maintainers do not acquire the habit 
of feeling the bearings of motors and of their dependent ma- 
chines when making the wiping-orf rounds. If they did, much 
expensive trouble would be avoided. The following experience 
illustrates what the proverbial "ounce of prevention" might 
have done in the way of saving a pound of cure. 

A freight elevator the electric equipment of which, though 
very old, had given years of satisfactory service began to blow 
fuses with such frequency as to become a nuisance. The motor 
and the control apparatus had been "gone over" several times 
and the commutator of the motor had been turned because 
sparking had roughened it. In the meanwhile the 25-amp. fuses 
had been replaced with 50-amp. fuses, which, while not to be 
commended, gave relief for a few days, then the outfit refused to 
do anything but blow fuses. 

An elevator man was sent for who disconnected the motor, 
tested it and found it in proper condition. Then with a bar he 
tried to turn the gears that the motor pinion had engaged, but 
could not do so. Inspection then disclosed that two bearings 
not far from the motor had "frozen fast." 

Rubbing of Rotor Will Cause Frequent Trouble. Ordinarily 
rubbing of the stator of an induction motor by the rotor is an- 
nounced by the fuses blowing, the frequency gradually becom- 
ing greater as the arc of the rubbing contact increases. In 
course of time, if the condition is not detected, the extra load 
imposed by the mechanical friction and the local heating due 
to the friction will result in damage that can be repaired only 
at great expense. The most common method of testing for bear- 
ing wear of small motors is to lift the working end of the rotor 
shaft up and down by hand to note if there is any knock. In 
doing this the stress should be exerted sideways as well as up- 
ward, because the greatest amount of wear does not always take 
place on the bottom of the bearing lining, In any event, if 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 189 

there is any knock at all the rotor should be removed and stator 
pole surfaces inspected for rubbed areas. 

In one case which came to the attention of E. C. Par ham a 
20-hp., 220-volt, three-phase induction motor was giving trouble 
due apparently to a hot bearing on the pulley end. The whole 
end of the motor would get too hot to touch, and it became im- 
possible to keep oil in the bearing on that end. The owner hesi- 
tated about stopping the motor because its continuance opera- 
tion was so important. Instead he tried to cool the bearing 
with a block of ice. Finally the fuses in the pole transformer 
that supplied the motor gave way. 

The first abnormal condition noted was that the motor was 
not protected by means of fuses. Furthermore, the transformer 
fuses were large enough for ten such motors. Inspection dis- 
closed that rubbing had worn some of the stator laminations 
almost through to the winding. Judging from the wear of the 
bearing on the other end of the motor, the excessive heating 
must have been due, not to a hot bearing but to the rubbing 
of the stator by the rotor. Fortunately, the stator winding was 
not injured, and after renewing the bearings on both ends of 
the motor normal operation was permitted again. The owner of 
the motor also hastened to order a fuse panel for his second- 
hand compensator. 

Motor Air Gaps and Allowable Bearing Wear. Failure of 
operators to appreciate the fact that the air gaps of small induc- 
tion motors are usually only a few thousandths of an inch often 
leads directly or indirectly to the trouble most common to these 
motors — rubbing of the rotor on the stator. Bearing wear 
equal to only the bearing clearance of direct-current motors will 
let the rotor down on the stator. Mr. Parham tells of one in- 
stance in which an inspector was called to look at a repulsion- 
induction motor on the inside of which sparks like those from 
an emery wheel occasionally could be seen. Inspection disclosed 
the fact that a very small area of the rotor which was not per- 
fectly cylindrical had been striking a few laminations that pro- 
jected from a part of the stator. Whether there would be con- 
tact or not depended on whether the rotor was at one end of its 
end-play travel or the other. In any event the pinion-end bear- 
ing lining had worn almost to the safe limit. If there had not 
been those few projecting laminations which gave a timely warn- 



190 ELECTRICAL AIDS TO GREATER PRODUCTION 

ing, the rotor probably would have been seriously damaged 
later. 

Causes of the Jerky Notching of Motors. One of the com- 
monest causes of jerky notching of motors is short-circuits in 
the resistance by means of which the motor is accelerated. Such 
short-circuits may be due to buckling of the resistance grids or 
to metallic foreign objects lying upon them. In either case 
acceleration will not be smooth. Another cause of unsatisfac- 
tory notching is the turning end for end of the frames of which 
the resistance as a whole is composed. The effect of such a 
reversal is to cut out small blocks of resistance on the lower 
controller positions and large blocks of resistance on the higher 
controller notches, where the motor is more sensitive to circuit 
resistance changes. 

In one instance the resistor of a three-phase induction motor 
was disconnected for repair because some of the resistance grids 
were broken and others were distorted until they touched one 
another. The electrician who did the disconnecting was as fa- 
miliar with the connections as he was with his own name, there- 
fore he did not bother to tag any of the removed wires. When 
the time came for installing the repaired resistance frames the 
man who had disconnected the apparatus was on sick leave and 
no one else knew anything about the connections. Serious 
trouble resulted. 

The moral of this experience, and of many other similar ex- 
periences, says Mr. Parham, is that when disconnecting any elec- 
trical device (it matters not how familiar one may be with the 
connections) the disconnected ends should always be marked or 
tagged in a very evident manner. 

Causes of the Balking of Induction Motors. Sometimes a 
rotor will start and sometimes it will not, even when the con- 
troller is moved to an advanced position. Rotors of the squirrel- 
cage type will be consistently unresponsive when starting under 
load if the conductivity of the end connections for any reason 
becomes impaired, and the maximum speed will be below nor- 
mal. Assuming that there is no rubbing, balking of rotors of 
the wound type generally is due to conditions not within the 
motor itself. Excessive load to be started or failure of a brake 
to release will cause any rotor to "hang" until a fuse blows or 
a breaker opens or until the controller reaches an advanced posi- 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 191 

tion. The first trouble is common to motors that drive rolls in 
which stock material becomes jammed. The second trouble 
may be due to low voltage, to want of proper adjustment of the 
brake clearance, or to baking of the brake coils. 

Among the more commonplace causes of balking of wound 
rotors, Mr. Parham points out, is bad and prolonged sparking 
due to overloads, to defective brush rigging or to rough or 
eccentric slip rings. This action will sometimes cause a non- 
conductive skin to form on the surface of the rings. A loose 
brush holder will prevent the brush from making certain con- 
tact, because with one direction of rotation the contact may be 
bad while with the reverse direction of rotation it may be good. 
Sticking of a brush in a holder will cause action similar to that 
experienced under the same condition with direct-current mo- 
tors. The starting becomes more and more erratic as the brush 
wears shorter and shorter, and finally one of the rotor circuits 
is opened by the brush failing to make any contact at all. 
Weak brush-tension springs and displaced tension fingers will 
cause irregular actions. Finally, ' disconnected, burnt-off or 
broken brush shunts have been known to affect seriously the 
promptness of starting and to cause brush-holder heating in 
normal operation. 

Cause of Trouble with Single-Phase Starter. When trouble 
with single-phase starters having connections like those shown 
herewith occurs, Mr. Parham says, it will usually be found that 
the contact a fails to touch both b and b 2 , or that there is an 




Fig. 71 — Simplified Diagram of Single-phase Starter Connections 



open circuit in the leads between these contacts and the motor. 
Failure of a to make contact with either b or b 2 may be due to 
a weak spring or blistered contacts. If any of the faults men- 
tioned exist, the production of a split-phase for starting the 
motor is prevented. 



192 ELECTRICAL AIDS TO GREATER PRODUCTION 

Large Air Gap Cause of Excessive Speed in Motor. During 
a lightning storm two field coils were burned out and the arma- 
ture was grounded on an interpole compound motor having a 
friction-saw blade mounted on the armature shaft. To save 
time, says R. L. Hearvey, the grounded armature coil was cut 
out and the two field coils were rewound. AYhen reassembled 
the armature ran 2300 r.p.m. at no load instead of 1900 r.p.ni., 
the increased speed causing the saw blade to wabble badly when 
sawing. The first test made was to determine if the shunt coils 
had the proper voltage drop across each and if their polarity 
was correct. Both were found to be right. The next test was 
to check the polarity of the compound field coils. This was done 
by opening the shunt circuit and starting the motor as a series 
machine. If the armature starts in the same direction as a 
series motor as it does as a shunt, the field coils are properly 
connected, as they proved to be in this case. This test requires 
considerable care as the field will be very weak and speed will 
reach dangerous proportions in a few seconds. 

The above tests showed the voltage drop across the shunt coils 
to be uniform and the polarity correct for both the shunt and 
compound windings; hence there could be but one other cause 
for the high speed at no load — that is, a weak field. As there 
was about 332-in. (2.1-mm.) clearance between the armature 
and the poles, sheet-iron shims 0.04 in. (1.23 mm.) thick under 
each pole were tried, which brought the speed down to 2000 
r.p.m. This was still too high, so the shims were increased to 
0.055 in. (1.78 mm.), which gave a speed of 1900 r.p.m. At 
this speed the motor has been operating satisfactorily for over a 
}ear. 

CHANGING HORIZONTAL MOTOR TO VERTICAL IN 

EMERGENCY 

"When the Xo. 1 Mine of the American Zinc Company of 
Tennessee at Mascot was accidentally flooded in the spring of 
1917 suitable pumps were immediately available, but vertical 
motors to drive them were not to be had any place in the dis- 
trict. Some horizontal motors were available, however, so it 
was decided to adapt these to vertical operation. The two im- 
portant problems that presented themselves were how to obtain 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 193 

a suitable thrust bearing to carry the rotor and how to lubricate 
the bearings in such a manner that the oil would not get into 
the windings of the motor. 

To support the rotor it was first necessary to splice the rotor 
shaft to make it extend through the end-shield. Accordingly a 
suspension stud was fitted to the shaft with a right-hand taper 
thread (the direction of rotation of the rotor was opposite). 
The body of the stud was made the same size as the motor shaft. 

kt*> Funnel 

I 

Oil Well- 



s' Pipe Bushing 
Oil Thrower 



Oil Pipe- 

FormK-60C 

ZFhase- 
2200.V-200 
Hp.ldOOR.p.m. 
61. Motor 



Y- Oil Well 

Suspension Nuf 
Bearing 
Suspension Stud 

Oil Collector 




Plate Motor 
Base 
OH Well 



Fig. 72 — Changes Made in Horizontal Motob to Permit Operation in 

Vertical Position 



while the upper end was threaded to receive the suspension nut 
which carried the rotor. For the thrust bearing a No. 715 
U. S. K. F. self-aligning ball bearing was selected. The inter- 
nal diameter of the ball races was considerably larger than the 
body of the stud, but a bearing of the right dimension to carry 
the load at this speed was not available, and in order to center 
the ball bearing a shoulder was turned on the suspension nut 
to take the upper ball race. This was made a snug fit and the 



194 ELECTRICAL AIDS TO GREATER PRODUCTION 

bearing performed nicely. The self-aligning washer rested on 
the end-shield, which was already machined. 

Arrangements were made to lubricate first the thrust bearing, 
then the upper motor bearing, and finally the lower motor bear- 
ing. An oil well was made of a short piece of 5-in. (12.7-cm.) 
pipe screwed into an 8-in. (20.3-cm.) channel to prevent any 
splash. The channel was bolted to the end-shield with U-bolts 
that were passed around the arms of the shield. A hole was 
drilled in the cover of the oil well to receive a funnel-shaped 
pipe, the bottom of which entered a hole in the suspension stud. 
The oil supply was taken from an overhead tank and regulated 
with a petcock. On entering the stud the oil was thrown into 
the balls of the thrust bearings through a %-in. (0.6-crnj hole. 
It was then dashed against the wall of the oil well by the re- 
volving parts of the thrust bearing, from which it trickled down 
into the upper motor bearing. 

To prevent oil running over the outside of the bearing bush- 
ing and consequently finding its way into the windings, a piece 
of 3-in. (7.6-cm. pipe was bored and turned to fill the space 
between the end of the bushing and the inside of the end-shield 
casting. The slots in the bushing for the oil rings were filled 
with babbitt metal. Oil following the rotor shaft is thrown off 
by a centrifugal device into an oil collector. From this point 
the oil is piped to the lower bearing. 

The oil-ring slots in the lower bearing were also filled with 
babbitt metal, and a hole was tapped in about the middle of 
the bushing for the oil pipe coming from the upper bearing. A 
spiral oil groove was cut in the babbitt to lead the oil to the 
upper end of the bearing, from which it was allowed to run 
down the shaft to an oil thrower. The oil which is drained off 
is filtered and used again. Albert Wettengal and R. P. Immel 
of the American Zinc Company of Tennessee worked out the 
foregoing arrangement. 

Home-Made Tools for Armature Repair Work. Oftentimes 
when considerable coil winding must be done certain minor 
tools are needed which cannot be purchased ready-made. These 
tools, however, are usually small and can be constructed in the 
shops. M. M. Clement has suggested several. The coil-taping 
needle illustrated herewith consists merely of 1 ft. (30 cm. of 
Xo. 1-i banding wire shaped so that it can be used for taping 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 195 



coils in closed-slot stators. After the user is accustomed to this 
device high speed may be attained. 

The coil raiser consists of a piece of steel, 16 in. by 1 by % 6 
in. (40.6 cm. by 2.5 cm. by 0.5 cm.) with a 4-in. (10-cm.) one- 
sided taper on one end for stripping open-slot armatures and 
stators. This also can be used to good advantage in removing 
grounded coils from a newly wound armature or in raising coils 
sufficiently to allow for insulating weak spots in the coils, the 





*? 



Plan 




coil raiser 

wire scraper 

Fig. 73 — Tools All Made from Common Stock 



k-VH. 



main object in this case being to lift out a tight-fitting coil with- 
out damaging the insulation. 

The wire scraper is very simply made and very economical, 
because it eliminates the use of a knife, whose life is short on 
account of the rough treatment accorded it. This device is made 
of spring metal, 12 in. by f in. by 1 / 1Q in. (30 cm. by 1.9 cm. 
by 0.2 cm.). The knife edges can be sharpened by means of a 
file and the tool used indefinitely. A section the shape of a 
rectangle is cut from the metal at the handle end, greatly in- 
creasing the spring effect of the device. 

For driving fiber wedges between the top of coil and the 
lamination overhang in closed-slot machines a wedge drift, made 
of a piece of tool steel, 8 in. by 5 in. by % 2 in. (20.3 cm. by 
12.7 cm. by 0.23 cm.), over which is fitted a loose-fitting steel 
sleeve, % 6 in. (0.16 cm.) thick, is very convenient. This is used 



196 ELECTRICAL AIDS TO GREATER PRODUCTION 

by inserting the fiber wedge about J in. (0.6 cm.) into the slot; 
then, with the drift pulled back into the sleeve, the sleeve is 
fitted over the wedge, which is driven into the proper place, the 
sleeve holding the wedge in position. 

Handling heavy armatures in the electric repair shops is 
often found difficult or awkward, on account of a lack of proper 
readj-made tools. An armature sling which is very simple to 
make consists of a piece of %6- in - (0.16 cm.) sheet iron, 2 ft. 
(61 m.) long by 10 in. (25.4 cm.) wide, with steel triangles 
attached to each end. These triangles, made of j-in. (1.9-cm.) 
steel bar which can be attached to the shop crane, eliminate any 
danger of the armature shaft breaking or springing. 



I< /e * 



WING NUTS- 



hETAL STRAIOMT HOSE . 



M ETAL STRIP- 



FILEHANDLE 



$fc FORGED 
" STEEL 



CELL SHARER 






OC3C 



BEVELLED 
KNIFEE DGE 



CELL CUTTER 



FASTENING 
RING 




10' 



TENSION WING NUT-,, I 

Qfc> i QPO 



I '4 FIBRE 

- 



'ty'HOLE 



l'4l\IBRE 




WIRE GUIDE 



i WIRE 
\\H0LE 
\ <X ; 

i J® e 

—to 




ARMATURE BANDING TENSION BLOCK 



SCREWSON 
LOWERHALF 
ONLT 



ARMATURE SLINC 



Fig. 74 — Tools are Simply axd Easily Made ix Repair Shop 



For shaping the fish paper in making cells for armature and 
stator slots the cell simper shown in Fig. 74 is very useful. It 
consists of two pieces of wood hinged together so that they will 
make a neat 90-deg. fold. The permanency of the correct-fold 
maker is insured by means of a metal strip attached to the 
wood slot. The cell shaper is used by inserting a piece of fish 
paper in the opening between the two blocks of wood, which 
is the length of the slot plus twice the height and whose width 
is the width of the slots. The metal straight edge, which is 
adjustable by means of wing nuts, allows the paper to be 
folded so as to be made the height of the slot. 

In cutting projecting insulations from slots of open slot 
windings after the coils have been assembled, the cell-cutter, 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 197 



which is composed of a piece of forged steel 14 in. (35.1 cm.) 
long by f in. (19 mm.) wide by % 6 in. (4.8 mm.) thick, with a 
set of beveled knife edges at one end and file handle at the 
other, has been found convenient. The shape of the device fa- 
cilitates the free movement of the cutting end. 

Another device which does away entirely with the necessity 
of a banding lathe in a small shop where the armature winder 
does its own banding saves considerable time and labor. This 
armature banding tension block, as shown in the illustration, 
eliminates the necessity of the armature being removed from 
the stand to be banded. About one foot of stout line with a 
hook attached to one end is made fast to the ring on the ten- 
sion block and hooked to an eye-bolt which is set in the floor 
for that purpose. The spool of banding wire is placed on a 
small stand beside the eye-bolt and the wire is passed between 
the two blocks at the rear end through the hole in the first 
wire guide over the tension curve and through the second wire 
guide hole and then to the armature. The tension can be 
regulated by the wing nut placed at the forward upper end 
of the block. By screwing down the wing nut both sides of 
the block are brought nearer together, thus narrowing the ten- 
sion curve over which the wire must pass. This increases the 
tightness of the band when a pipe wrench is used to revolve the 
armature. 

Device for Winding Coils of Any Shape. A device that 
was developed by Frank Huskinson for forming coils of prac- 
tically any shape is shown in the accompanying illustration. 



30"- 




''Bo/f, A/uf"' A V 
ancfWasfier 



g Hole off Center 




Disks,.- 
Z"D.K±"+hick 



Fie. 4 
K//">i</% 3"—x 



^ yiiTiIi[^ 



■fSf'd. Thread 

fig. 3 



andWasher 
Fie.l F»&-2 

Fig. 75— Framework for Winding Different Shape Colls 



It consists merely of an iron framework fitted with several flat 
disks. By loosening the nuts (B) in Fig. 75, the two long rods 
can be adjusted vertically- to give any width of coil within the 



198 ELECTRICAL AIDS TO GREATER PRODUCTION 

limits of the device. Plat disks attached to the ends of each 
member of framework, as shown in Fig. 75, may be adjusted 
along the length of the rods to give the longitudinal dimensions 
of the coil to be wound. The wire is then wound around these 
disks. 

The device can thus be arranged for nearly all shapes of 
coils and can be made in permanent form for winding a num- 
ber of the same size coil. The coils can be easily removed by 
loosening several of the disks. 

Switching Arrangement for Testing Motors. The arrange- 
ment of switches shown in Fig. 76 will be found useful in motor 
repair shops for testing purposes. By means of this arrange- 



To MOTOR TEST' 



TRANSFORMER HO. k, | 



<— O 

<•— o 
■►— o 




o— t 
o 



o— J 



t 



TRANSFORMER ISO. 2 



r— O 

O 




<— o 



O-" 



SECONDARY 

TRANSFORMER 

COILS 






110 VOLTS 



220 VOLTS 



440 VOLTS 



Fig. 76 — A Switch Arrangement That Will be Found Useful for 
Testing Motors in Eepair Shops 



ment single or three-phase 110, 220 or 440-volt energy may be 
tapped from a pair of transformers connected in open delta, 
merely by switch operation, thus saving considerable time in 
changing connections to suit the various motors under test. 

The installation requires a pair of transformers having 110- 
220-440-volt secondaries. Such transformers are sometimes 
constructed with eight secondary leads, sometimes with only 
four. In the latter case four special leads must be brought 
out, as it is necessary to have access to both terminals of each 
of the four secondary coils. The extra leads can be readily 
brought through porcelain bushings placed in holes drilled in 
the transformer covers. 



MOTORS, CONTROL, SPECIFIC APPLICATIONS 199 

It will be noted that the full capacities of the transformers 
are utilized at the standard voltages. In addition, a variety 
of single-phase voltages are obtainable across the outside leads 
for special testing by connecting the two transformers for dif- 
ferent voltages. 

This switching combination is not foolproof. Either trans- 
former may be short-circuited by incorrect connections, but the 
arrangement is so simple that any tester soon becomes accus- 
tomed to it. 

Standard single-pole, single-throw knife switches are in- 
stalled, but half of the switches are used double-throw. If the 
handles of the switches which are used strike the bases of the 
others, the handles may be offset to clear laterally. The instal- 
lation may be somewhat improved by the insertion of additional 
single-pole switches at points A, although these are not absolutely 
essential. 



CHAPTER IV 

ILLLUMINATION— SELECTION OF EQUIP- 
MENT, ECONOMIES, AND SPE- 
CIFIC APPLICATIONS 

ARTIFICIAL DAYLIGHT IN THE INDUSTRIES 

Artificial illuminants which are generally adaptable to indus- 
trial lighting are usually so deficient in certain colored rays 
(notably the blue and violet) that many colors can only be 
distinguished with difficulty or are so distorted as to be un- 
recognizable to the eye trained to discriminate under natural 
daylight. These facts are easily demonstrated by experiment, 
and the importance of color in industrial lighting may be read- 
ily ascertained by observation. 

The future will bring forth special illuminants for the pur- 
pose of aiding vision in various ways, but in the present article 
only the uses of artificial daylight will be discussed by M. Luc- 
kiesh of the Nela Research Laboratory, National Lamp Works, 
Cleveland. 

Comments on Actual Installations. For the most accurate 
color discrimination north-sky light is generally used, and an 
artificial-daylight unit giving this quality of light is often called 
a color-matching unit. For less accurate color work noon sun- 
light is satisfactor}^, and artificial daylight units emitting light 
of an approximate noon sunlight quality are available both 
as an accessory to an ordinary illuminant and as the "Mazda 
C-2" lamp. The wide application of the latter, which ap- 
proximates noon sunlight in integral quality, is proof that it is 
unnecessary to approximate daylight quality more closely than 
is required by the color-perceptive ability of most individuals. 
North-sky-light quality when emitted by an artificial lighting 
unit is generally considered too "cold" owing to the preju- 
dices arising from continued association of a "warm" color 
with artificial light. Examples of the installations of the 

200 



ILLUMINATION— SELECTION OF EQUIPMENT 201 

latter quality of artificial daylight will be drawn from a large 
number of installations of these units. These units will be 
termed sunlight units for the sake of brevity in expression. 

Color Factories. — North-sky-light units are in use for the 
more accurate color discrimination and color matching, and 
sunlight units are employed for general illumination of proc- 
esses less exacting in the requirements of color perception. 
The products of such factories when exhibited in stores or used 
in paint shops are also at present illuminated in many cases 
by means of approximate daylight units. 

Paint Shops. — North-sky-light units for accurate color mix- 
ing and for the standardization of colors are used in consider- 
able numbers, but in general in this field the approximate day- 
light units are used. The final product is well displayed under 
such illumination, and as a consequence many automobile dis- 
play rooms, for example, are illuminated by these general- 
lighting units. 

Textile Mills. — In dye mixing and testing, many color- 
matching units are in use at the present time. Eows of such 
units are also used parallel to the perches upon which the dyed 
materials are hung. An angle unit is found necessary in many 
cases in order to illuminate the material, which hangs vertically 
and is inspected by the light transmitted as well as by that 
which is reflected by the material. In accurate dyeing even the 
most experienced colorist who is thoroughly familiar with the 
spectral characteristics of his dyes is often unable to be sure 
of his ground without an illuminant of daylight quality. The 
sunlight units, or those emitting light roughly approximating 
daylight in quality, have found many applications in various 
textile mills. The same difficulties in discriminating the colors 
of textiles persist in the wholesale and retail stores, so that many 
of these establishments have been equipped with various types 
of artificial daylight units. 

Garment Factories. — Both types of artificial daylight have 
been applied to these industries, including woolen mills and 
cotton mills. 

Cotton Exchanges. — Although the discrimination of different 
qualities of cotton is included in the foregoing classification, 
this activity deserves special mention. Raw cotton is sorted 
into a vast variety of grades and the color is an important 



202 ELECTRICAL AIDS TO GREATER PRODUCTION 

factor. The colors vary from a white to a yellowish white, and 
the tints are so weak in color that it is quite impossible to dis- 
criminate many of them from each other under ordinary yel- 
lowish artificial light. The more accurate artificial daylight 
illuminants are in use for this work. 

Furs. — All the difficulties of color discrimination are met in 
the fur industries. Not only do the lighter tints present diffi- 
culties under ordinary artificial light, but especially the dark 
shades which are so commonly encountered in furs. Artificial 
daylight units are also being installed by wholesale and retail 
furriers. 

Color Printing. — In mixing inks and in inspecting proof many 
color-matching units are employed. For the presses the approxi- 
mate daylight units find wide application. An interesting fea- 
ture of artificial daylight in color printing, besides the satisfac- 
tory rendition of the blues, violets and purples, is the resulting 
contrast of yellows upon white backgrounds under this quality 
of light. Under ordinary artificial daylight it is very difficult 
to distinguish the yellow impression on white paper in three- 
color printing. Pressmen find great difficulty in distinguish- 
ing flaws under such conditions, which often results in consid- 
erable spoilage. In lithography, art work on the original draw- 
ing and the work on stones is now being favorably done in many 
places under artificial-daylight illuminants. W all-paper dis- 
plays are well illuminated by the sunlight units, hence the latter 
have found their way into wholesale and retail wall-paper stores 
to a great extent. 

Art Studios. — Many installations of artificial daylight have 
been made in studios of pure and applied art. Oddly enough, 
artificial daylight of a sunlight quality is often preferred, not- 
withstanding the general choice of natural north-sky light for 
such studies. This seeming contradiction is likely to lead one 
astray if further inquiry is not made. North exposure has not 
been chosen in general by artists for the sake of the quality or 
color of the light but because north-sky light is the most constant 
natural daylight both in intensity and quality of spectral char- 
acter. Some discerning artists prefer to paint from models in 
the "warmer" light in order to have their paintings tend toward 
the warmer tone. 

Metal Work. — The discrimination of the various colors of such 



ILLUMINATION— SELECTION OF EQUIPMENT 203 

alloys as brass and commercial gold is very difficult under ordi- 
nary yellowish artificial light because the various mixtures ap- 
pear nearly if not exactly the same in color. Under artificial 
daylight the differences are readily distinguishable. Difficulties 
arise with other metals and alloys in which color discrimination 
is of considerable importance. The sunlight units are usually 
satisfactory in these cases. Lacquering is often more satisfac- 
torily done under light of daylight quality. 

Ore Refineries. — Color plays an important part in the selec- 
tion and judgment of ore concentrates, and as a consequence 
this field has been invaded by artificial daylight units. An ore 
with a bluish-gra3 r tint appears gray under ordinary yellowish 
artificial light, and a yellowish ore cannot be distinguished easily 
if at all from another specimen of a gray or yellowish tint. In 
the former case the specimen is found to be a blue-gray under 
artificial daylight, and in the latter case the yellows are easily 
distinguished. An actual case encountered in practice is the 
presence of yellowish pyrites in lead or zinc concentrates. 

Chemical Analysis. — In such work color discrimination is 
often of importance. The requirements vary so that either the 
north-sky-light or sunlight units are satisfactory, depending 
upon the case. In titrating, the north-sky-light units appear to 
be more satisfactory. The concentration of a weak solution is 
sometimes estimated by the color of a considerable depth of the 
solution. An example of this is the yellowish color of chlorine 
solutions. When of low concentration this yellowish tint can 
be distinguished with difficulty if at all under ordinary artificial 
light. 

Laundries. — Dirt, spots due to scorching and other blemishes 
which are generally yellowish in color are more readily distin- 
guishable under artificial daylight than under ordinary artificial 
light. "Bluing," which is used to neutralize the yellowish tint 
of white fabrics, can be applied with more certainty under arti- 
ficial daylight. The approximate daylight units are usually 
satisfactory in laundries. 

Paper Mills. — In the manufacture of paper the problems of 
distinguishing delicate tints of approximately white papers and 
of tinting pulp to match certain standards are commonly met. 
Artificial daylight has met. these problems satisfactorily. 

Flour Mills. — In a similar manner various types of artificial 



204 ELECTRICAL AIDS TO GREATER PRODUCTION 

daylight units are in use for distinguishing the delicate tints of 
flour. 

Sugar Refineries. — Accurate color-matching units are in use 
for distinguishing the colors of sugars. 

Jewels. — Color is an important factor in the value of jewels. 
The illuminant influences the colors of jewels quite markedly. 
Diamonds present special difficulties because commercial dia- 
monds vary in color . from blue-white to a decidedly yellowish 
tint. The former lose their bluish tinge and the latter appear 
less yellow under ordinary artificial light. The more accurate 
artificial daylight illuminants are desired for purposes of exami- 
nation of jewels. Pearls and opals often lose some of their 
beauty under ordinary artificial light owing to the suppression 
of the blues and violets and to the shifting of the pinks toward 
red. 

Dentistry. — Matching artificial teeth, cements, porcelain in- 
lays, etc., presents difficulties both in factories and in the dental 
offices. North-sky-light units are in use for the more exacting 
work, but the sunlight units are found quite satisfactory for 
much of the work. 

Medicine and Surgery. — Artificial daylight has found its way 
into hospitals and private offices for use in surgical operations 
and in diagnosis. Various types of units are in use, depending 
upon the requirements and upon desires of the users. It is dif- 
ficult to distinguish the various tints of healthy and diseased 
tissue, and manifestations of skin diseases are sometimes unre- 
vealed under yellowish artificial light. 

The foregoing are only a few of the activities in which artifi- 
cial da} T light units have been installed. The different activities 
are far more numerous and include other classes of stores, show 
windows, barber shops, hair-dressing establishments, tailor shops, 
art galleries, etc. Many unique and unexpected applications 
have been met in practice, and it appears that the field for such 
lighting units will be greatly extended. Instances have been 
found in which users have declared that a light of a daylight 
quality is easier on the eyes for close work than yellowish light. 
In the absence of a decisive method of testing this point such 
statements must be given some attention, especially because they 
present a reasonable possibility when viewed from the stand- 
point of evolution and adaptation. 



ILLUMINATION— SELECTION OF EQUIPMENT 205 

One of the most prominent features is the miscibility of arti- 
ficial daylight with natural daylight. There appears to be an 
unsatisfactory condition of lighting when natural daylight must 
be reinforced with yellowish artificial light. As a result of this 
many installations of artificial daylight have been made in offices, 
drafting rooms, etc., where the discrimination of the colors of 
objects is of little or no importance. In all of these applica- 
tions esthetic taste is a secondary consideration. Where this is 
a primary factor the scientific aspect, which this article bears 
upon, is subordinated. There are ways of using artificial' day- 
light and yet satisfying the esthetic taste, but these cannot be 
discussed in this article. 

SPEEDING UP MANUFACTURING BY IMPROVING 

ILLUMINATION 

Results of tests which have been conducted by engineers of 
the Commonwealth Edison Company to determine quantitatively 
the effect upon industrial output of increased and improved 
illumination were outlined in a paper entitled "Production 
Lighting Intensities," read before the recent convention of the 
Illuminating Engineering Society by William A. Durgin. The 
ninety-three plants thus far surveyed total 17,400 employees, 
cover a floor area of 96 acres and aggregate a lighting load of 
1420 kw. While the survey was largely inspectional, listing the 
number, style and condition of units used, and applying arbi- 
trary utilization factors to obtain the intensities produced, very 
considerable confidence is felt in the average results, which show 
a mean of VA ft.-candles now in use with variations from 0.01 
ft.-candle to 10 ft.-candles and an average consumption of 0.33 
watt per square foot and 80 watts per employee. For these 
same plants the I. E. S. code would provide an average intensity 
of 5.5 ft.-candles, 3.66 times the present level. The intensity 
would vary from 2 to 12 foot-candles ; the average watts per 
square foot would be 1, and the watts per employee 240, or three 
times the present consumption. 

In order best to explain the method of making tests and to 
indicate results thus far obtained the original paper is quoted 
as follows: 

"Such tests are much more difficult than at first thought ap- 



206 ELECTRICAL AIDS TO GREATER PRODUCTION 

pears. Our revised program contemplates a four months' run — 
the first month with the equipment as it exists, the second with 
proper equipment to give 50 per cent higher intensity than the 
maximum recommended by our code, the third month at the 
lower code level for ordina^ practice or what is generally con- 
sidered good present practice, and the fourth again at the higher 
or productive intensity level. For such a test the plant pro- 
duction records must be accurately kept and a fair percentage 
of the work must be done in hours of darkness. The chief diffi- 
culties are two — (1) to find plants with adequate production 
record systems, and (2) to induce the plant to return to the 
lower level of intensity at the end of the second month of the 
run after the advantage of good lighting has been once experi- 
enced. 

"One test was run in a machine shop producing soft metal 
bearings, operations ranging from rough to fine. Only two 
months of the program were run, but in the month at which the 
intensity was maintained at 12 ft. -candles production in the 
several operations was increased from 8 to 27 per cent over that 
of the previous month, when an intensity of 4 ft.-candles was 
used. In this instance general lighting with deep-bowl reflector 
equipment was employed for both intensities and every precau- 
tion taken to eliminate commercial bias. The superintendent 
was so impressed with the value of the higher intensity that he 
had it extended to the other floors of the building. 

In the second accurate test the program could not be fol- 
lowed carefully, the comparison being between bare lamps on 
drop cords and a properly designed reflecto-cap installation. 
The new equipment gave about twenty-five times the intensity 
previously used and showed an increased production of from 
30 to 100 per cent in the several operations of a large pulley 
machine shop. Again the superintendent was enthusiastic. 

In the other nine plants it has been impracticable to run tests, 
but in every case the superintendents and owners are fully con- 
vinced of the truth of our statement that the average effect will 
prove at least a 15 per cent increase in production at an in- 
creased cost of not more than 5 per cent of the payroll. 

"To get results quickly it is impracticable to secure the abso- 
lutely best equipment for each installation. In our own company, 



ILLUMINATION— SELECTION OF EQUIPMENT 207 

therefore, we have adopted definite specifications employing 
three general types of equipment : 

"1. Gas-filled lamps with steel reflectors and eye shields in 
the 200, 300 and 500-watt sizes. 

"2. Gas-filled lamps with deep-bowl reflectors for extreme 
mounting heights. 

"3. Vacuum lamps and deep-bowl reflectors for certain drop- 
cord applications. 

' ' Our effort is concentrated upon the first class. In using these 
it is of first importance that the shields be sealed in place and only 
removable by the foreman or other authorized employee, for the 
ordinary workman believes but one part of the code. He wants 
more light, but he knows nothing of the effect of excessive 
brightness contrasts and if left to himself will remove the shield 
as a useless obstruction. Recent installations of all three units 
are equipped with such sealing wires. 

' ' Of the three we are especially emphasizing the 300-watt unit. 
It has an efficiency of some 84 per cent, a maximum brightness 
of 7500 millilamberts on the interior of the diffuser ring, and is 
well adapted to installation on present outlets. In many plants 
it is hardly possible to rewire now ; in others it is very question- 
able whether such rewiring is warranted. But with this unit 
giving its maximum candlepower at the 50 deg. angle it is en- 
tirely practicable to produce reasonably uniform lighting with 
spacings of 14 ft. to 16 ft. (4.2 m. to 4.8 m.) at mounting heights 
from 10 ft. to 16 ft. (3 m. to 4.8 m.). 

"Where 12 ft. to 18 ft. (3.6 m. to 5.4 m.) mounting heights 
above the floor are possible, spacings as high as 20 ft. (6m.) 
can be used with the 500-watt unit, with an acceptable result in 
uniformity of intensity and diffusion of light. This unit has an 
efficiency of 77 per cent and a maximum brightness of 2300 
millilamberts, the view of the interior of the ring being largely 
cut off by the blades. Again it may be emphasized that our 
object is not ideal illuminating engineering ; it is practical ap- 
plication with as little change in wiring as possible. In these 
installations we are to secure productive intensity quickly at 
minimum expense with equipment which will continue to supply 
that intensity during its life. 

"Of primary importance, therefore, is the ease with which 



208 ELECTRICAL AIDS TO GREATER PRODUCTION 

such equipment can be maintained. With drop-cord units, bare 
or shaded by the tin dirt collectors, even the extremely serious 
defects in intensity produced and brightness contrasts permitted 
are hardly as important as the extreme inefficiency which re- 
sults after the machine has spattered them with oil or the work- 
man has manipulated them with dirty hands. We have tested 
several such units taken directly from factories and have found 
the utilization efficiency less than 25 per cent. ' ' 

EFFECT OF LIGHTING ON ACCIDENTS, SPOILAGE 
AND PRODUCTION 

To be sure, the application of electric power to America's 
industries has made it possible to increase production in many 
plants; however, the effect of lighting", though perhaps less 
apparent, is none the less important. 

With this thought in mind, the Electrical World canvassed a 
large number of the leading manufacturing and industrial plants 
in the United States in order to show as concretely as possible 
the value of good lighting. In all of the plants electric light in 
one form or another is employed. In a majority of the reports 
it was stated that new lighting systems had recently been in- 
stalled, and in not a few cases it was stated that different forms 
of lighting were continually being tried out in order to get the 
best artificial lighting arrangement possible. It was particularly 
noticeable that manufacturers are changing from the inefficient 
carbon lamp to the tungsten lamp, and particularly to the gas- 
filled unit. Another change which is prevalent is from arc 
lamps to tungsten incandescent lamps. 

The reports showed a disposition to depart from the use of 
bare lamps, and in quite a few cases it was reported that lamp 
candlepower was considerably increased. Instances were also 
noticed of changes from clusters to single lamps. 

Better Spirit of Labor with Good Lighting. Manufacturers 
were asked in cases where changes in lighting had been made 
whether there was any noticeable effect on the workmen. In 
most cases no effect was noticed, but this cannot be taken at its 
face value. Manufacturers generally are sold on the benefits of 
good lighting and do not take the trouble to investigate the ef- 
fects for the sellers. In a large number of instances, however, 



ILLUMINATION— SELECTION OF EQUIPMENT 209 

it was noticed that the workmen showed a better spirit and went 
at their work in a happier frame of mind when the lighting 
conditions were improved. The efficiency of employees was also 
better. 

One factory making molded insulation on changing from car- 
bon and arc lamps to tungsten and gas-filled lamps with re- 
flectors noticed an increased output on the benches of 75 per 
cent. A sugar mill changing from carbon to tungsten lamps 
with reflectors noticed an increase in output of the night shift of 
20 per cent, besides eliminating bad batches of sugar. 

The great value of lighting to-day is its effect upon labor and 
therefore upon output both in quality and quantity. In this 
connection a superintendent of one of the largest explosives 
plants in the United States said: 

"Since in our munition plants we are operating night and 
day, the question of lighting is an important one. In fact, one 
must have good lighting in order to keep up our production, 
avoid accidents and produce better esprit de corps." 

There are any number of shops where every minute of oc- 
cupied labor counts in the production. Consequently the ele- 
ment of man-hours assumes an importance not previously known. 
An accident, with the resulting loss in time by one or more 
operators injured, is no longer a dollars and cents proposition 
but rather one of output. Besides, when an accident occurs it 
is not only the injured who lose time. The psychological effect 
on the other workers is such that considerable time is lost and a 
large part of the day's output of those near the accident is lost 
through spoilage due to nervousness. 

Accidents Decreased. It is apparent that anything tending 
to decrease industrial accidents has a very real value in increas- 
ing the production of a plant. That lighting is in the category 
of an accident preventer is evident from the replies received. 

In one plant a new system of lighting so reduced the number 
of accidents that the company decided to carry its own insur- 
ance. A company engaged in the manufacture of zinc concen- 
trates states: 

"We have a remarkably small number of accidents, although 
more than 1000 men are employed. We attribute part of this 
to adequate lighting, which is in line with the safety first idea." 

A leather manufacturer states : ' ' Improved lighting naturally 



210 ELECTRICAL AIDS TO GREATER PRODUCTION 

lessens accidents, particularly around elevators and machinery." 

A statement from a plant milling low-grade copper is to the 
effect that "Light exposes danger. Good lighting is insurance 
against accidents." 

Another copper-concentrate plant says : ' ' We believe that 
better lighting has done its share in reducing our accidents more 
than 50 per cent." 

Xot only does better lighting prevent much of the loss of time 
resulting from accidents but also that resulting from poor health. 
With good and adequate lighting it is possible to keep the plant 
cleaner and more sanitary and to reduce eye strain and head- 
ache. 

That good lighting helps to build up esprit de corps seems 
undebatable. ' The men are happier, take more pride in their 
work and in the appearance of the shop, and generally do better 
all around when the light is good. It also undoubtedly has its 
effect on keeping labor turnover from going higher. It is very 
doubtful if a few cents more wages will tempt skilled men from 
a plant that is well lighted to one that is poorly lighted. 

Production Increased and Spoilage Reduced. There seemed 
to be a unanimity of opinion regarding the part good light plays 
in increased production, although there were no figures to sub- 
stantiate the opinion. However, it had been noticed in many 
plants that the men start work more promptly in the mornings 
and work up nearer to quitting time. Less loafing has been no- 
ticed in plants that have installed better artificial lighting. As 
one manufacturer put it, ''A poorly lighted mill makes the men 
sleepy and production suffers." One or two others instanced 
men going to sleep in dark places where the lighting was poor. 
In each case, however, this practice was eliminated by the instal- 
lation of a better lighting system. 

Spoilage and repairs are elements to be considered in any pro- 
duction program. The reduction of the former has a twofold 
significance to-day. It reduces production and also reduces the 
available amount of raw materials. Anything, therefore, which 
tends to lessen spoilage increases production and economy. 

Manufacturers seem unanimous in. expressing their convic- 
tions that better artificial lighting means less spoilage. A state- 
ment from a copper mill is to the effect that good lighting "is a 
necessity in cutting out excessive waste of copper through the 



ILLUMINATION— SELECTION OF EQUIPMENT 211 

tails." A manufacturer of glazed kid states that better light- 
ing has "lessened to a considerable amount the number of mis- 
takes. ' ' 

Another angle is brought out by the general manager of a 
rubber plant who states that good lighting "helps the inspec- 
tion department to throw out more bad pieces which otherwise 
would get shipped to customers to send back." The other side 
of this situation is, of course, the lessening of the burden on 
transportation systems by just so much. 

A manufacturer of motors points out that good lighting re- 
duces spoilage very much where the workman is working to 
micrometer dimensions. 

A sugar-mill operator states that "good lighting reduces 
spoilage to a minimum in our case. It used to be 'quite a fre- 
quent occurrence to add cane juice to the ocean brine because 
of the overfilling and consequent overflowing of juice tanks, a 
thing that has been reduced through better lighting to prac- 
tically nothing. The splashing and spilling of the massecuite 
about the centrifugal driers has been reduced to a minimum, 
thus making for less spoilage and a cleaner plant. While exact 
figures of the saving thus brought about cannot be given, it is 
safe to say that the saving pays for the whole lighting system in 
one season. The saving in lubricants due to the reduction of 
spillage amounts to 25 per cent." 

A tire manufacturer states that, unless lighting for inspection 
is of the best, tires that should be rejected for defects are passed 
up. 

In a number of cases the value of good lighting in making 
repairs was mentioned. Mention was also made of the fact that 
good lighting made it possible to catch irregularities in a ma- 
chine operation sooner than would otherwise be the case. 

There is a unanimity of opinion therefore among manufac- 
turers on the value of good artificial lighting. The results of 
better lighting can be seen in increased output, fewer accidents, 
reduced spoilage and steadier labor. 

LIGHTING ECONOMIES 

While only about 2^ per cent of the total coal output of the 
United States (700,000,000 tons) is consumed in the production 



212 ELECTRICAL AIDS TO GREATER PRODUCTION 

of artificial light, any part of this that is saved through lighting 
economies will assist in the conservation of coal. In view of 
this fact the committee on war service of the Illuminating Engi- 
neering Society, 1 at the request of the Fuel Administration 
through the National Committee on Gas and Electric Service, 
has compiled some very valuable suggestions on "War-Time 
Lighting Economies''' in the form of a bulletin. Limiting the 
use of artificial light to the minimum necessary number of hours 
per day and promoting the most efficient use of artificial light 
during those hours are the general methods proposed. In vari- 
ous places it is suggested that local lighting companies be con- 
sulted. 

Discussing the problem more in detail, the I. E. S. committee 
on war service points out that unnecessary lighting can be elimi- 
nated by inakinsr the maximum use of davlight and bv avoiding 
useless lighting. Dirty glassware and fixtures, dark ceilings and 
walls and inefficient lighting equipment are also productive of 
waste. Excessive or extravagant lighting must be curtailed. 

Fallacies to Be Avoided. There are certain fallacies which 
must be guarded against in effecting lighting economies and the 
committee refers to these saying : 

Removing reflectors or shades from lamps in order to "get more 
light" defeats the object. The raw light from glaring bare lamps is less 
effective than a smaller quantity of reasonably diffused light not ex- 
posed to the eye. 

Attempting to economize by reducing the number of lamps or by 
nsing smaller lamps indiscriminately is unwise. In nearly every case 
ample illumination is essential to useful accomplishment. The most 
successful conservation is elimination of waste of light, not reduction 
of use of light. 

In war time human energy and financial resources are to be con- 
served as well as fuel. Except in the greatest emergency it is un- 
wise to save a little coal at the expense of waste of lahor or inipair- 

1 Underlying the accepted principles of illumination are requirements for 
safety, conservation of vision, esthetics, comfort, convenience and economy. 
The Illuminating Engineering Society is committed to the preservation of 
these principles and to their application in lighting practice in the public 
interest. A number of recommendations here presented, particularly those 
advocating decreased use of light, are calculated to save fuel rather than to 
bring about most desirable illumination conditions. These are to be re- 
garded solely as a war measure, justifiable in the present emergency, but 
otherwise not to be approved. 



ILLUMINATION— SELECTION OF EQUIPMENT 213 

ment of health or menace to the safety of the public. Coal saved 
through the improvement of lighting equipment is clear gain. To 
diminish lighting standards in industrial plants, offices and other places 
where accomplishment depends in part upon vision is to reduce ac- 
complishment or output. In such places, therefore, lighting should 
not be reduced. On the contrary, an increase in the standard of lighting 
may be the truest economy and in the best interests of the nation. The 
liberal use of light for protection of important property, munition 
factories, public works, etc., is likewise in the public interest, and under 
present circumstances no attempt should be made to save fuel through 
the reduction of such lighting. 

In an acute local fuel situation an absolute lack of fuel may result 
in largely curtailed activities. If there is no fuel, industry must cease. 
Such a critical situation obviously demands radical curtailment of 
lighting beyond anything which is contemplated for general adoption. 

In certain localities in the height of winter there may be a power 
shortage due to abnormally taxed generating capacity. This likewise 
may necessitate local lighting restrictions of a more extreme character. 

In either event, when such a situation occurs, the problem is a local 
one, the handling of which must be governed by the particular circum- 
stances. 

Maximum Use of Daylight Saves Energy. Referring to the 
use of daylight, the committee says : 

Refracting and diffusing glass in windows helps to spread the light 
to distant parts of the room. 

Carry out operations requiring strong illumination near windows 
where plenty of daylight is available. Arrange machinery, furniture, 
etc., so daylight falls on objects to be seen, not on eyes. 

Whitened surfaces on building exteriors (especially about courts of 
high buildings) give more and better daylight in opposite buildings. 
These may reduce the period of artificial lighting by several hours each 
day. 

Keep windows and skylights clean. Dirty windows may absorb half 
the daylight. 

Dust window screens frequently. Remove them as soon as the in- 
sect season is passed. They absorb one-third of the daylight. 

Use light-colored ceilings and walls wherever practicable to conserve 
daylight and artificial light. 

Areas at a distance from windows often require artificial light when 
natural lighting is sufficient near the windows. Connect the switches, 
if possible, so that the light sources may be turned on in rows parallel 
with the windows, and the artificial lighting thus used in the several 



214 ELECTRICAL AIDS TO GREATER PRODUCTION 

sections only as is necessary. Place the responsibility of operating 
these switches on designated individuals. 

Useless lighting caused by failure to turn off lamps when not 
needed is also a great cause of waste and can be eliminated to a 
great extent by inviting the cooperation of the occupants of the 
place, attendants, etc. This will be discussed later with relation 
to different installations. 

Maintaining the most efficient use of artificial lighting requires 
in. the first place the employment of the most efficient lighting 
units ; second, their proper location ; third, the correct applica- 
tion of reflectors and shades ; fourth, a high utilization factor, 
and, fifth, proper maintenance of the equipment and reflecting 
surfaces. 

Efficiency and Location of Lamps Important. With relation 
to the type of lighting unit to use the committee says : 

Large lamps are usually more efficient than small lamps, and where 
practicable installation should be altered to consist of the fewest lamps 
from which uniform illumination may be obtained under the conditions 
of use. Where clusters of lamps are employed under shades replace 
them by a single larger lamp with suitable reflector. 

Do not use electric lamps of the carbon-filament type where the more 
efficient tungsten-filament lamps can be employed. These substitu- 
tions will result in a saving of three-fourths of the fuel used for a. 
given candlepower. 

An intelligent choice of lamps makes it possible to reduce the con- 
sumption of fuel. 

Lamps should be spaced to give uniform lighting and with reference 
to the work so as to avoid bad shadows. This permits the use of the 
minimum wattage in the general lighting and makes it possible to re- 
move most drop lamps and local lighting. The latter are objectionable 
from the conservation point of view because they may be left burn- 
ing when no necessity exists. 

Factors Governing Use of Shades and Reflectors. Regarding 
the general use of shades and reflectors the report reads : 

Modern lamps are so brilliant that they may injure the eyes if used 
without protective equipment. Shades and globes conceal them from 
view, soften the light, and where desired redirect a considerable part 
of the light in the direction needed. Shades and globes never increase 
the total quantity of light, but an efficient reflector will usually increase 
the light where it is needed. With such a reflector a smaller lamp may 



ILLUMINATION— SELECTION OF EQUIPMENT 215 

suffice, thus saving coal. The advice of the lighting company should 
be sought when selecting such equipment. 

Flat reflectors allow much of the light to escape to the walls instead 
of directing it to the work. They also leave the bright light source ex- 
posed to view and the glare interferes with the vision, causing a demand 
for still higher intensities. Use reflectors of the dome or bowl shapes 
for greatest economy. Except where lamps are mounted in high bay 
areas use bowl-frosted lamps to reduce glare reflected from the work 
and to soften the shadows. Be sure that reflectors are deep enough to 
protect the eye from the glare of the filament. 

Do not use indirect or semi-indirect lighting fixtures in conjunction 
with dark ceilings which absorb a large part of the light. 

Light- Colored Walls and Ceilings Save Energy. As a rule, 
at least one-half, and sometimes practically all, of the light util- 
ized in interiors is received by reflection from walls and ceilings. 
Good light-tinted paint when fresh rarely reflects more than one- 
half of the light which falls upon it. The proportion of light 
reflected from good white lead and oil paint under average con- 
ditions diminishes by about 10 per cent a year. The same is 
true of calcimine and similar coatings. It is apparent therefore 
that there is an opportunity for improving lighting efficiency 
through the employment of the best finishes for ceilings and 
upper walls. Painting white ordinary light-tinted surfaces may 
increase the light reflection by as much as 50 per cent. There- 
fore in order to save fuel in lighting wherever it is practicable 
paint ceilings white, employ light tints for the upper parts of 
walls, and use paint that is non-porous and easily cleaned. 
Light-colored surfaces reflect five to ten times as much light as 
dark surfaces. 

Cleaning Too Often Overlooked. Maintenance of lighting 
fixtures and reflecting surfaces such as walls, ceilings, etc., is so 
often neglected that particular attention should be directed to 
it as a means of saving fuel. The report on "War-Time Light- 
ing Economies" reads: 

The loss of artificial light due to dirty glassware and dark or dingy 
ceilings and side walls ranges from 30 to 50 per cent and may be 
avoided by renovation at necessary intervals. With indirect or semi- 
indirect lighting the refinishing of the ceiling and cleaning of the light- 
ing units will frequently increase the intensity 50 to 100 per cent, per- 
mitting a reduction in wattage to the next lower size of lamp. 



216 ELECTRICAL AIDS TO GREATER PRODUCTION 

Keep lamps and reflectors free from dust by a regular schedule of 
cleaning at short intervals. 

Suggestions Applying to Industrial Plants. The foregoing 
suggestions apply to all places and may be considered the funda- 
mental requirements of economical lighting. However, many 
places have conditions which are peculiar to them so additional 
factors have to be considered. A few of these that apply to in- 
dustrial plants are given below : 

Industrial Plants. 1 — In almost every plant there is waste in the use 
of light, the elimination of which can be accomplished without retard- 
ing production, impairing the vision or menacing the safety of the 
employees. So far as possible do all lighting from a general over- 
head system out of the control of individual workmen. Make some in- 
dividual in each department responsible for seeing to it that lamps 
are lighted only in such areas and for such periods as necessary. 

STANDARDIZING FACTORY LIGHTING 

The considerable increase in night work which has resulted 
from the war lays particular emphasis on the importance of 
the artificial lighting of factories. The efforts to standardize 
suitable lighting for industrial establishments therefore has di- 
rect value at the present moment. The I. E. S. code of 1915 was 
a long step in advance and served as a basis for some important 
legislation. The experience of the last three years, together with 
the greater amount and severer requirements of factory lighting, 
has rendered changes desirable. These were undertaken last 
year by the I. E. S., and their importance has been emphasized 
by recent legislation. Changes in the original code have been in 
considerable degree due to the greater importance now attached 
to artificial illumination and to a considerable degree have been 
in the direction of a more complete classification of the work to 
be done. Another ver} T important change has been to direct 
more specifically attention to the question of glare, always recog- 
nized as a very important factor in successful industrial light- 
ing, but hard to reduce to workable definitions. Indeed, whether 
it is possible to draft a regulation of a kind practicably enforce- 

i For information in regard to good factory lighting practice consult the 
"Code of Lighting Factories, Mills and Other Work Places," Illuminating 
Engineering Society. 



ILLUMINATION— SELECTION OF EQUIPMENT 217 

able which will properly cover the subject of glare is a question 
which does not yet admit of a definite answer. 

A longer step forward is made in the strong recommendation 
of actual measurements of the lighting by a portable photo- 
meter. At the present time instruments of this kind, of suffi- 
cient accuracy for the purpose and convenient for use, are 
readily attainable, and there is no reason why legislation as to 
industrial requirements cannot be worked to a successful result. 
The four desiderata in industrial lighting suggested by the com- 
mittee on labor of the Advisory Commission — to wit, conserva- 
tion of eyesight, safety, increased labor efficiency and better 
quantity and quality of output — are the obvious things to be 
borne in mind in codes and statutes. As regards the general 
conditions of lighting, those which satisfy the last two require- 
ments will also satisfy the first two, with due attention to the 
lighting of stairways and other areas of that kind. 

If the minimum lighting requirements are specified in accord- 
ance with the suggestions of the I. E. S. and can be enforced, 
as is comparatively easy by the use of portable photometers, the 
whole situation will be effectively cleared up. Heretofore it has 
been far easier to say whether lighting was or was not good than 
to pin it down to definite intensities of illumination. Now, with 
the problem of photometry somewhat simplified, the necessity of 
training state factory inspectors in the use of instruments and 
in the fundamental principles of industrial lighting becomes 
obvious. At present they will have much less difficulty than was 
the case a very few years ago, since manufacturers are com- 
pelled to do much work by artificial light and have come rather 
generally to realize at last the importance of good illumination 
as a factor in the general success of the plant. Very little pres- 
sure intelligently applied by legislation and its judicious en- 
forcement will work wonders. 

New Industrial Lighting Code for Wisconsin. As a result of 
the appointment of an advisory committee to consider the revi- 
sion of shop-lighting orders of the Industrial Commission of 
Wisconsin, a new code was adopted which is much more specific 
in its provisions and thus more readily understood and enforced. 
John A. Hoeveler, illuminating engineer of the Commission, 
says : All technical terms used are defined for the benefit of 
factory superintendents. More definite specifications provide 



218 ELECTRICAL AIDS TO GREATER PRODUCTION 

for adequate light distribution for various classes of work, tak- 
ing* into account daylight as well as artificial illumination, and, 
for the elimination of objectionable glare, the brightest square 
inch of visible light source permitted is 75 cp. for overhead 
lighting and 3 cp. for local lighting. 

In order that all interests might be represented and thus given 
the opportunity of advancing constructive criticism, the advisory 
committee was made up of ten members, including the superin- 
tendent of a lamp-manufacturing factory, the manager of a gas 
company, the illuminating engineers of a central station, of the 
city of Milwaukee, of the United States Public Health Service 
and of the Industrial Commission, the chief electrician of a 
manufacturing plant, the works manager of a manufacturing 
plant, an electrical contractor and an oculist. 

This advisory committee at its first meeting did little more 
than decide that the shop-lighting orders of the Industrial Com- 
mission, in effect since 1913, should be repealed and an entirely 
new code adopted, patterned after the Illuminating Engineering 
Society "Code of Lighting for Factories, Mills and Other Work 
Places, ' ' and the similar codes of Pennsylvania and New Jersey. 
It was also decided to solicit the assistance of prominent illumi- 
nating engineers, both in and outside Wisconsin, and of the com- 
mittee on lighting legislation of the I. E. S., of which L. B. 
Marks of New York is chairman. 

Concerning the proposed new orders, the committee recom- 
mended that "the scope of the new orders be extended to in- 
clude all portions of industrial plants — (1) roadways and yard 
thoroughfares; (2) stairways, passageways, aisles, storage 
spaces; (3) manufacturing spaces; (4) offices. 

The parts of the new code, as recommended by the committee, 
which differ from provisions of other industrial commissions are 
specified as follows : 

The new lighting code differs from the 1913 orders and many 
existing codes in that it defines terms used; definitely specifies 
the intensity of illumination to be provided at the work for the 
different classes of work (the unit of illumination employed is 
the foot-candle) ; provision is made for adequate properly ap- 
plied natural illumination (a feature other states have not 
adopted as yet) ; shading of lamps is mandatory under certain 
conditions which are recognized to be bad when lamps are per- 



ILLUMINATION— SELECTION OF EQUIPMENT 219 

mitted to be exposed, and thus provision is made to minimize 
glare; the distribution of light on the work must be reasonably 
uniform; emergency lighting is required; pilot or night lights 
and easily accessible control are specified ; and maintenance is 
made mandatory. 

The committee states as its opinion "that these orders, if 
adopted, will make it possible to secure lighting in industrial 
plants which will reduce avoidable accidents, and if the indus- 
trial commission, through its deputies, will urge employers to 
provide the intensities of ordinary practice, working conditions 
will be greatly improved to the benefit of both employer and 
employee. ' ' 

Although the committee agreed that all new buildings prefer- 
ably should be constructed so as to make proper provision for 
adequate natural lighting, it was also agreed that this frequently 
is impossible (no matter how much glass area may be provided) 
in congested districts. Therefore a general requirement (Order 
2110) was worded so that either natural or artificial light may 
be used. Obviously it is to the advantage of the owner to utilize 
as much natural light as possible, and when the code is pub- 
lished 1 by the industrial commission it is proposed to include an 
appendix which will point out the advantages of natural illumi- 
nation and briefly discuss economical means of securing it in 
adequate intensity, properly applied. 

Illumination Intensities Specified. The illumination inten- 
sities at the work, specified for different classes of service in 
Order 2112, are the same as recommended by the I. E. S. com- 
mittee on lighting legislation, with the exception of "(d) 
Toilets and Washrooms," which was added at the suggestion of 
Mr. Hoeveler, after having seen it included in a draft of proposed 
lighting standards for federal industrial establishments formu- 
lated by the Bureau of Standards. The committee felt that 
toilets and washrooms were important enough spaces in the in- 
dustrial plant to warrant a separate specification, as all too fre- 
quently these are the darkest and most unsanitary parts of a 
factory. 

1 The code is now in print. 



220 ELECTRICAL AIDS TO GREATER PRODUCTION 

Extracts from the Wisconsin Lighting Code. 
Order 2112— Artificial Light. 

When the natural light is less than twice the minimum permissible in- 
tensities of illumination set forth in the following table, artificial light 
shall be supplied and maintained in accordance with the table. The 
intensities of recommended practice indicate the desirable illumination 
for best working conditions. 



ILLOIIXATIOX INTENSITY AT THE WORK IX FOOT CANDLES. 

Minimum Permissi- Ordinary 

ble Intensity Practice 

(a) Roadways and yard thoroughfares 0.02 0.05- 0.25 

( b) Storage spaces 0.25 0.5 — 1.0 

(c) Stairways, passageways, aisles 0.25 0.75-2.0 

(d) Toilets and washrooms 0.5 1.5-3.0 

(e) Rough manufacturing, such as rough ma- 

chining, rough assembling, rough bench 

work, foimdry floor work 1.25 2.0 - 4.0 

(f) Rough manufacturing involving closer dis- 

crimination of detail 2.0 3.0 - 0.0 

(g) Fine manufacturing, such as fine lathe work, 

pattern and tool making, light colored tex- 
tiles 3.0 4.0 - S.O 

(h) Special cases of fine work, such as watch- 
making, engraving, drafting, dark-colored 
textiles 5.0 10.0 -15.0 

(i) Office work, such as accounting, typewriting, 

etc 3.0 4.0 - S.O 



Xote. — The measurements of illumination are to be made at the work 
with a properly standardized portable photometer. 

This table of lighting intensities required in industrial processes with 
the exception of part (d) was issued by the Illuminating Engineering So- 
ciety and subsequently adopted by the United States Bureau of Standards 
for the Xational Safety Code and government plants. With the same ex- 
ception the table has likewise been incorporated in the factory lighting 
codes or regulations issued by several of the state industrial commissions. 

The minimum foot-candles specify the lowest illumination intensity with 
which the employees can be expected to work with safety when artificial 
light is used. It is to the advantage of the employer to provide the in- 
tensities of the ordinary practice, as this results in less eye strain, greater 
accuracy of workmanship, increased production for the same labor cost and 
less spoilage. When part daylight and part artificial illumination is used, 
it is desirable to use even higher intensities than those of ordinary prac- 
tice in the table above. < See note accompanying Order 2111 in Code.) 

In order that the illumination intensities shall never fall below the mini- 
mum during the interval between inspections, installations should be de- 
signed to produce initial values at least 25 per cent higher. 



ILLUMINATION— SELECTION OF EQUIPMENT 221 

Order 2113 — Shading of Lamps for Overhead Lighting. 

Lamps suspended at elevations above eye level less than one-quarter 
their distance from any position at which work is performed must be 
shaded in such a manner that the intensity of the brightest square inch 
of visible light source shall not exceed 75 cp. (See appendix of Wis- 
consin Code for method of measuring brightness.) 

Exception. — Lamps suspended at greater elevations than 20 ft. above 
the floor are not subject to this requirement. 

Note ( a ) . — Glare from lamps or unduly bright surfaces produces eye 
strain and increases the accident hazard. , 

The brightness limit specified in this order is an absolute maximum. 
Very much lower brightness limits are necessary in many interiors illumi- 
nated by overhead lamps, if the illumination is to be satisfactory. In some 
cases, the maximum brightness should not exceed that of the sky (2 cp. to 3 
cp. per square inch.) 

Note (b). — Where the principal work is done on polished surfaces, such 
as polished metal, celluloid, varnished wood, etc., it is desirable (but not 
mandatory at present) to limit the brightness of the lamps in all down- 
ward directions to the amount specified in this order. 

Order 2114 — Shading of Lamps for Local Lighting. 

Lamps for local lighting must be shaded in such manner that the in- 
tensity of the brightest square inch presented to view from any position 
at which work is performed shall not exceed 3 cp. 

Note. — In the case of lamps used for local lighting, at or near eye level 
the limits of permissible brightness are much lower than for lamps used for 
overhead lighting, because the eyes are more sensitive to strong light re- 
ceived from below, and because such light sources are more constantly in 
the field of view. 

Order 2115 — Distribution of Light on the Work. 

The reflectors or other accessories, mounting height and spacing em- 
ployed with lamps shall be such as to secure a reasonably uniform dis- 
tribution of illumination, avoiding objectionable shadows and sharp 
contrasts of brightness. If local lighting is used, there shall be em- 
ployed in addition a moderate intensity of overhead lighting. 

Exception. — Where the light from the local lamps falls principally upon 
surfaces which are white or nearly so and the ceiling and walls of the room 
are light, there is often a sufficient general illumination received indirectly 
by reflection to obviate the necessity of additional overhead lighting. 

Note. — When local lighting is used as the sole source of illumination of 
an interior, the field of illumination from each lamp is in contrast to the 
surrounding darkness, thereby causing eye strain and increasing the acci- 
dent hazard. 

Order 2118 — Maintenance. 

All lighting equipment and windows shall be periodically cleaned, 
inspected, kept in order, and when defective replaced, so that the in- 



222 ELECTRICAL AIDS TO GREATER PRODUCTION 

tensities of illiiniination will never fall below those specified in Order 
2112. 

The reduction of harmful glare with artificial lighting sys- 
tems occupied much attention on the part of the committee. 
As mentioned by Prof. C. E. CTewell in the Electrical World 
some time ago, 1 the Wisconsin advisory committee was of the 
opinion that the I. E. S. glare specification ("Lamps shall be 
suitably shaded to minimize glare",) is too indefinite, and that a 
more definite rule would aid the inspectors who are called upon 
to determine when the limits of glare are exceeded. The glare 
specification, as embodied in Order 2113 (/'Shading of Lamps 
for Overhead Lighting") and Order 2111 (''Shading of Lamps 
for Local Lighting";, is the outcome of correspondence with the 
I. E. S. committee on lighting legislation and a sub-committee 
which was appointed to investigate this matter and of which 
Ward Harrison was chairman. 

The committee fully realized that the glare rule adopted may 
require revision after being tried out. but that is the reason the 
State of Wisconsin has abandoned making safety and sanitation 
laws by statute and instead has created an industrial commis- 
sion and given it full powers to issue orders which have the legal 
force of statutes on these subjects. The state government real- 
ized that advances in industry bring about change in conditions 
of employment, and that an elastic method of dealing with such 
changes would be the only successful one. The I. E. S. con- 
tinued the above mentioned sub-committee to cooperate with the 
Industrial Commission, and it is expected that this cooperation 
will result in gaining more information on this important prob- 
lem. Although the advisory committee knew that there was not 
sufficient knowledge to state definitely the maximum allowable 
brightness permissible, it was convinced that the maximum set 
was not unreasonable. 

Since opaque metal or mirror reflectors are chiefly used in the 
industries of Wisconsin, this requirement will insure good eye 
protection because of the fact that for locations coming within 
the scope of the rule reflectors which screen off all light within 
approximately 11 deg. below the horizontal of necessity will be 
used. 

i "Changing Aspects of Factory Lighting Legislation," Vol. 71. Xo. 13, 
p. 666. 



ILLUMINATION— SELECTION OF EQUIPMENT 223 

When glass reflectors are used they must be dense enough to 
reduce the brightness to less than 75 cp. per square inch. Light 
sources of lower brightness than 75 cp. per square inch, as, for 
instance, mercury-vapor lamps with a brightness of but 14.9 cp. 
per square inch, may be used exposed ; but, as explained in the 
accompanying note, conditions of individual installations m!ay 
require the shading of light sources of even such low brightness. 

As regards the distribution of light on the work, the advisory 
committee considered the wording "a good distribution of light 
on the work" of the I. E. S. code too indefinite, and, as men- 
tioned by Professor Clewell in the article previously referred 
to, several attempts were made to make the rule more definite. 
Finally the matter was settled by wording the rule as in Order 
2115 ("Distribution of Light on the Work"). The term "rea- 
sonably uniform distribution," it was felt, would give the in- 
spectors a better idea of what is considered satisfactory light 
distribution. Local lighting only is not permitted, except where 
the light from the lamps falls principally upon light surfaces 
and where the ceilings and walls are light under which condition 
there is often sufficient general illumination. 

The question of emergency lighting caused much difference 
of opinion among the committee members. All were agreed that 
some emergency lighting is necessary, but that the necessity 
varies much with the different industries, that large plants need 
it more than small plants, and that the character of emergency 
lighting which may be secured at reasonable cost varies consid- 
erably in different localities. A general rule (Order 2116) was 
agreed to, but it was considered essential that explanatory notes 
be included in an appendix to indicate what the Industrial 
Commission would consider satisfactory compliance with the 
order. 

Maintaining the Equipment. When all is said and done re- 
garding the proper requirements of a lighting system, either 
natural or artificial, and the factory is properly equipped, of 
what use is the lighting if it is not maintained ? To meet this 
objection, Order 2118 ("Maintenance") was included in the 
code. The committee realizes that this provision can be en- 
forced much less rigidly than the others, because the Industrial 
Commission has too few inspectors to make it possible to visit all 
the factories at frequent intervals, as would be necessary if the 



224 ELECTRICAL AIDS TO GREATER PRODUCTION 

maintenance of the lighting were to be checked up. In fact, an 
inspector at present can hardly cover his territory in a period 
of a year. 1 

However, if when the inspector visits a plant, he finds 
the lighting facilities poorly maintained, he will be clothed 
with the authority to order a general clean-up and replacement 
of defective equipment. It is calculated that this will in time 
help matters, especially in view of the fact that the inspectors 
'do their work in a cooperative way and spend much time edu- 
cating the plant superintendents and foremen in safety, sanita- 
tion, lighting, ventilation, welfare and supervision of male, fe- 
male and child labor and in arbitrating disputes between em- 
ployer and employee. 

The various orders were read and discussed at a public hear- 
ing in Milwaukee, and practically no objections were raised. 
On the other hand, some favorable comments were expressed. 
On May 20 the Industrial Commission adopted the code, which 
took effect on July 1, 1918, for new construction and will be 
effective on July 1, 1920, for additions to existing lighting sys- 
tems. Replacements of existing systems not in accordance with 
the code must be prosecuted as rapidly as circumstances permit. 
In the latter matter the Industrial Commission will exercise its 
best judgment as to how rigidly to enforce the provision. When 
these orders are published in bulletin form, which is being done 
now, it is proposed to include an appendix which will discuss 
each order in detail and suggest how it may be complied 
with. The purpose of this appendix will be to assist architects, 
electrical contractors, shop superintendents and electricians 
who design lighting installations to interpret the code 
properly. 

i The Wisconsin inspectors do their work in an intensive manner. Each 
factory inspected is given careful study. Meetings of the foremen are 
called, at which the imsafe practices of the plant are discussed and reme- 
dies suggested. The foremen are made to realize that it is their duty to 
instruct their men how to perform their work safely, to see that machines 
are guarded, that the shop is sanitary and that the many other require- 
ments of the commission are carried out; that these requirements have been 
drafted by committees of practical shopmen and experts in various lines, 
only upon due consideration, and that as a result they represent what is 
considered a minimum to make the conditions of employment better. Con- 
sequently fewer factories are visited each year than if the work were con- 
fined merely to looking for violations of the commission's orders and issuing 
an order for the correction of the violation. 



ILLUMINATION— SELECTION OF EQUIPMENT 225 

THE EFFECTIVE APPLICATION OF PROTECTIVE 

LIGHTING 

Edmund Leigh, chief of plant protection, Military Intelli- 
gence Bureau, has stated that of the important means of pro- 
tection against fires, explosions and sabotage in our industrial 
establishments, utilities, storage and forwarding systems, the 
value of lighting and its effective application are least appre- 
ciated and understood. An inspection of numerous plants and 
a consideration of current recommendations in this field of illu- 
mination confirm Mr. Leigh's statement and suggest the desir- 
ability of emphasizing the points covered in the following notes 
by H. H. Magdsick. 1 

A protective lighting system to be effective must be compre- 
hensive. The chance of trouble from within a plant is no less 
than that from without. Therefore, in the majority of instal- 
lations provision should be made to light not only the bound- 
aries and approaches, but every part of the yards and all inte- 
rior spaces, so that no one can approach the plant from the 
outside or attempt to work destruction anywhere within its 
limits without being easily observed by armed guards or loyal 
employees. Occasionally the guards may be so stationed that, 
while themselves concealed in a shadow or dark area, sufficient 
surfaces about them will be lighted so that any one passing 
where no light falls directly upon him will nevertheless always 
be between a guard and a well-lighted surface and will there- 
fore be distinctly outlined in shadow. More often the safe and 
practical way is to light every part of the plant. 

The intensity of illumination which is provided must be ade- 
quate to meet conditions of visibility which are short of the 
ideal. The amount of light required in a clear atmosphere must 
be considerably increased to be effective when haze or smoke is 
present. A higher intensity is necessary when street lamps, 
brightly lighted windows or other sources are in the field of 
vision than when the background is always black. If the build- 
ings are dark, more light is required than when their surfaces 
have a high reflection factor. An intensity entirely too low to 
reveal a menace quickly is one of the most common deficiencies 

i Engineering Department National Lamp Works of General Electric 
Company. 



226 ELECTRICAL AIDS TO GREATER PRODUCTION 

in yard and boundary lighting. By providing illumination 
generously the drain on man power for guarding purposes is 
greatly reduced. 

Ineffective Distribution of Light a Fault of Many Installa- 
tions. Much of the expenditure for protective lighting is wasted 
because the light is ineffectively distributed and directed. In 
general, illumination should be obtained at every point from 
more than one unit and from more than one direction. Bad 
shadows will thus be obviated and the failure of individual lamps 
will not leave large areas unprotected. Glare often nullifies the 
value of lighting. Particularly is this true where one encoun- 
ters exposed sources or the direct beams from projectors at a low 
mounting height. To facilitate vision, glare should be mini- 
mized so far as possible by using accessories which shield the eye 
from the light source or by mounting units high above the usual 
line of vision. Diffusing globes reduce the contrast in bright- 
ness between the source and its background and thereby lessen 
the glare somewhat in interiors or when placed near light walls 
of buildings. Their glare-reducing value is slight, however, 
when they are viewed against a black background such as usually 
obtains out of doors, for the ratio of brightness is not greatly 
reduced. 

Several types of equipment employed extensively for protec- 
tive lighting are listed in Fig. 77. In selecting any of the equip- 
ments for out-door service one should be careful to secure well 
constructed, weatherproof fixtures. In a few cases the deep- 
bowl type of enameled steel reflector is of value in giving the 
maximum protection against interference with vision. Usually 
the dome type gives ample protection and is to be preferred 
because of the wider spread of light and greater output. In 
order that glare may be reduced with prismatic refractor fix- 
tures, they should be ordered with the socket so placed that the 
maximum candlepower is delivered at angles from 15 deg. to 
20 deg. below the horizontal. The intensity at angles near the 
horizontal will then be greatly reduced. 

It may be noted that floodlighting units are available for a 
wide range of beam spread, permitting a selection to meet varied 
requirements. With the specially concentrated filaments of the 
floodlighting lamps, accurate control of the light is possible, so 
that beams of small as well as large angular divergence can be 



ILLUMINATION— SELECTION OF EQUIPMENT 227 

obtained. The projectors shown at c and d in Fig. 77 are de- 
signed for use with such lamps. Equipments illustrated in a 
and ~b, which employ the regular multiple lamps pendent in the 
reflector, do not permit confining the beam to so narrow an 
angle because of the greater area of the light source. 

The percentage of light directed into the beam varies greatly. 
Two characteristics determine the efficiency of projectors — the 
reflection factor of the surface and the depth of the reflector, 
i.e., the percentage of the light from the lamp intercepted. Mir- 
rored glass is becoming the standard reflecting surface, for it has 
a high efficiency which can be permanently maintained. The 
reflection factor is from one-fourth to one-third greater than that 
of the polished aluminum and nickel surfaces commonly em- 
ployed in metal-reflector units. 

Searchlamp and Floodlamp Requirements Are Different. A 
large number of floodlighting projectors are still sold with shal- 
low parabolic reflectors, directing only 18 to 25 per cent of the 
light into the beam. This condition exists because many design- 
ers have followed searchlighting practice without differentiating 
between floodlight and searchlight requirements. In designing 
or using searchlamps one is concerned only with securing the 
highest possible intensity at the center of the beam. It is de- 
sirable to suppress the light radiating at wide angles from the 
center of the beam so that the observer watching the distant 
illuminated area from his station near the searchlight may suffer 
the least interference with vision. The spread of the beam is 
determined by the angle which the light source subtends at the 
reflector; hence best results are obtained by using a paraboloid 
of relatively long focus, and therefore shallow, for a given 
diameter. In floodlighting one is concerned with delivering as 
large a percentage of the light from a lamp as possible to an 
area at a relatively shorter distance and viewing this area at 
closer range. Therefore a greater divergence of beam is usually 
required and the scattered light does not become detrimental, 
but on the contrary is frequently useful. 

For most floodlighting it is possible to employ the deeper 
reflectors with contours formed and combined in such a manner 
as to redirect a large proportion of the light from the lamp. 
Such deeper projectors are illustrated, for the ordinary multiple 
and floodlighting lamps respectively, in b and d of Fig. 77. 



228 ELECTRICAL AIDS TO GREATER PRODUCTION 

The common practice of employing the shallow paraboloid with 
the ordinary multiple lamps of large light source, as in a, is 
obviously very wasteful, when with an intelligent design it is 
possible to increase the output in the beam by from 50 to 100 
per cent. 

With the possible exception of the opal-globe equipments, all 



EQUIPMENT FOR PROTECTIVE LIGHTING 



ACCESSORY 




IP I DOME TYPE 

ENAMELED STEEL 
v . REFLECTOR 




AN6LE TYPE 
ENAMELED STEEL 
REFLECTOR 



LAM P 



Mazda B and 
Mazda C; Multiple 
of all sizes to 
1000 watts 



Mazda B and 
Mazda C; Multiple 
of all sizes to 
1000 watts 




PRISMATIC 

REFRACTOR 

FIXTURE 




OPAL GLOBE 
UNIT 



FLOOD-LIGHTING 
PROJECTOR 




BEAM-SPREAD 
3°-15° 



BEAM-SPREAD 
12-24° 



BEAM -SPREAD 
40°- 50° 



BEAM SPREAD 
15-50° 



Incandescent 
Searchlight 



Mazda Cj Multiple 

of 75 to 1000 watts 

Mazda C series 

of 60 to 1000 

candlepower 



Mazda B and Mazda 
C, Multiple of all 
sizes to 1000 watts 
Mazda C series of 00 
to 1000 candlepower 



Mazda C flood-lighting 
BOO and 400 watts 



Mazda C flood -lighting 
ZOO and 400 watts 



Mazda C flood-lighting 
400 watts 



Mazda C; Multiple 
300 to 1000 watts 



Highly concentrated 
filament Mazda C 



PER CENT OF LIGHT 
FROM LAMP DELIVERED 
BELOW HORIZONTAL 



75 ~ 60 



<bO 



65 



60 - 70 



35 - 50 



PER CENT OF LIGHT 
FROM LAMP DELIVER- 
ED IN BEAM * 



20-40 



30 - 50 



40-45 



20 - 40 



1,000,000 to 5,000,000 
Beam candlepower 



* In addition, some light is emitted at wider angles directly from thelc 
or scattered from the reflector This may sometimes also be useful 



lamp itself 



Fig. 77 — Types of Equipment Extensively Used for Protective 

Lighting 



types of units listed in Fig. 77 can be used advantageously 
under many conditions, although each is better adapted than the 
others for certain applications. Many people have come to 
regard floodlighting units as the one type of equipment suited to 
protective service. The fact that they are relatively, new and 
that they opened up new possibilities in lighting seems to have led 



ILLUMINATION— SELECTION OF EQUIPMENT 229 

to an exaggerated estimate of their performance and value. 
From Fig. 77, it is apparent that a projector mounted at a 
remote point actually delivers less light to a given area than 
would be secured from ordinary types of equipment in this area. 
However, it does not follow that the latter are always to be pre- 
ferred ; due weight must be given to other factors as well. The 
relative advantages of lighting with floodlamps and with dis- 
tributed systems of the other types of lighting units may, in a 
general way, be summarized as follows : 

Floodlighting Versus Distributed Systems. Dome and angle 
enameled-steel reflectors and prismatic refractor fixtures must 
be distributed at moderate spaeings on supports relatively near 
the area to be illuminated. This distribution of units results in 
the marked advantage that at a given point light is usually re- 
ceived from several lamps and from different angles, thus obvi- 
ating dangerous shadows and minimizing the effect of the outage 
of an individual lamp. Such equipments are efficient and their 
cost is relatively low. To mount the fixtures, however, it is 
sometimes necessary to erect additional poles or other supports 
and extend the lighting circuits. 

With projectors a different practice may be adopted, for the 
control of light in narrow beams gives the advantage of mount- 
ing equipment at a few favorable points, often on existing cir- 
cuits, and delivering the light to areas at a distance. Thus the 
cost of additional poles and wiring is frequently saved, but this 
advantage is usually more than offset by the relatively high 
cost of the projectors themselves and the somewhat lower utiliza- 
tion of light flux. This is particularly likely to be the case if a 
sufficient number of lamps are installed at different points to 
eliminate long, sharp shadows. Furthermore, it is difficult to 
arrange floodlamps so that objectionable glare will not at times 
be experienced, nullifying much of the value of the light. Nev- 
ertheless, when they can be carefully located and mounted high 
on pole brackets, platforms or roofs of buildings excellent light- 
ing may be secured. The outage of individual projectors is 
likely to be far more serious than that of a unit of the other 
types in a more distributed system; also, where a number of 
projectors are mounted on a platform there is danger that all 
of the lighting for a large area may be put out at once. Flood- 
lamps are particularly valuable for providing light quickly in 



230 ELECTRICAL AIDS TO GREATER PRODUCTION 

an emergency, for supplementing the ordinary systems and 
temporarily reinforcing the intensity at certain points. They fill 
a great need in illuminating locations in or near which no wiring 
can be carried or no supports placed for the older types of light- 
ing fixtures. 

At one plant located directly on a city street angle enameled- 
steel reflectors with 300-watt lamps are attached to the building. 
For mounting heights of 25 ft. (7.6 m.) or more, and spacings 
not more than twice the height, this system is a desirable one, 
although sometimes it may be improved by tilting the units in 
slightly to minimize the glare. Where the building surface is 
light and for lower mounting heights, dome reflectors are prefer- 
able, spaced not more than three times their height. 

Dome reflector fixtures with 200-watt units mounted 20 ft. 
(6 m.) above the pavement reinforce the street lighting. On 
the building face are two angle units which help to illuminate 
the space in front of the building and assist the watchman in 
identifying persons approaching the plant. A similar installa- 
tion of dome reflectors is carried on the pole line along the fence 
bounding another side of this property. In either case the spac- 
ing should not be more than four times the height of the units. 
Higher mounting is advantageous ; a height lower than 20 ft. 
(6m.) is likely to be objectionable except for lamps as small as 
100 watts. When cars are left standing adjacent to a building, 
units should be added along the face to prevent deep shadows. 

Dome reflectors like those just referred to but equipped with 
100-watt to 500-watt-lamps are also particularly suitable for 
protecting the boundaries of large inclosures. Prismatic re- 
fractor fixtures are also desirable for this service. They illumi- 
nate a wider zone, and the spacing may be increased to eight 
times the mounting height. The largest sizes of lamps are there- 
fore often employed with such equipment. 

When projectors are used to protect an inclosure one edge of 
the beam is directed along the fence, allowing the patrolman to 
walk inside in comparative darkness. The projectors are placed 
12 ft. (3.6 m.) above the ground, one every 200 ft. (60.9 m.), 
and the beams pointed in one direction around the inclosure. 
So long as the patrolman is able to walk in the direction in which 
the projectors are pointing, conditions for vision are excellent. 
If, however, it becomes necessary for him to turn around and 



ILLUMINATION— SELECTION OF EQUIPMENT 231 

face the units, the glare he experiences will make the lighting 
ineffective. Therefore it is better to mount the projectors high 
on pole brackets or elevated platforms. When they can be placed 
30 ft. to 60 ft. (9.1 m. to 18.2 m.) above the ground the inter- 
ference from glare is very greatly minimized. 

An error which is commonly made is to space projectors at too 
great a distance. The range is rapidly reduced as the atmos- 
phere becomes hazy; also the outage of a unit becomes more 
serious as the spacing is increased. Where mounted low, as in 
the illustrations, the maximum spacing recommended is about 
250 ft. (76.2 m.), and this value should be reduced for the 
widest-angle units. Under favorable conditions, where the pro- 
jectors are mounted high and the largest lamps are employed, 
the spacing may be increased. 

For lighting the yard proper, various types of accessories 
may be utilized. Angle reflectors attached to the buildings may 
be employed to light adjacent spaces, if mounted 25 ft. (7.6 m.) 
or more above the ground. Dome reflectors and prismatic re- 
fractors on brackets attached to buildings, poles distributed 
throughout the yard, etc., meet the requirements best in the ma- 
jority of properties. When floodlighting projectors can be 
placed sufficiently high and at various points so as to deliver 
light from several angles, good results may be obtained by their 
use. However, there is always danger that glare will not be 
sufficiently minimized and that piles of material or other ob- 
structions in the yard will cast long, dark shadows, creating an 
accident hazard and affording a place of concealment. With a 
greater number of smaller wattage lamps in dome reflectors dis- 
tributed about the yard, these dark shadows are eliminated and 
the guard is able to detect the intruder. The conditions could 
also have been improved if projectors had been directed at this 
point from both sides. 

Narrow-angle floodlamps on building roofs or elevated plat- 
forms are valuable in lighting long approaches to a plant or 
sweeping open fields or waterfronts about a property. Incan- 
descent-lamp searchlights greatly increase the range. With one 
of these the attendant will be able to "pick up" a man at dis- 
tances as great as one-half mile (8 km.). Occasionally it is of 
value to have a beam which is wider horizontally, while any 
greater spread vertically would be wasted. Under these condi- 



232 ELECTRICAL AIDS TO GREATER PRODUCTION 

tions a piece of factory-ribbed glass may be substituted for the 
clear-glass cover, resulting in a band of light of wide horizontal 
divergence but little vertical scattering. The intensity at the 
middle of the beam and the range of the unit are of course con- 
siderably reduced. 

STANDARDIZATION OF LIGHTING CAN EXPEDITE 

SHIPBUILDING 

The admirable efforts which have been expended toward expe- 
diting the building of ships should not be relaxed just because 
peace has been declared. Great opportunities are opened along 
this line by the standardization of the electrical equipment for 
the temporary lighting of vessels under construction, particu- 
larly where the same or similar types of ships are being built. 
This work may be divided into three subdivisions, says William 
G. Hexamer, who was formerly electrical engineer of the Chester 
Shipbuilding Co. : 

1. The permanent wiring on the permanent ways, which can 
be so constructed as to cover almost any electrical demand. 

2. The lighting of vessels which have not as yet reached the 
stage of construction where a regular standardized temporary 
system can be installed. 

3. The regular temporary wiring system, which must be so 
constructed that it can be repeatedly used from one vessel to 
another without much more than minor changes. 

Considering these subjects consecutively, permanent ways can 
be wired from a three-wire 110-220 volt system.. At the Chester 
(Pa.) Shipbuilding Company's plant it has been found advis- 
able to run three No. 2 mains from a junction box at the head 
of the ways through 1%-in. (3.16-cm.) conduit to a point where 
the water line makes it impracticable to continue. This covers 
practically two-thirds of the ways. At 20-ft. (6-m.) intervals in 
this line are installed YX condulets each containing a three to 
two-wire double-branch cutout fitted for 30-amp. plug fuses. 
Two No. 8 wires feed a Q. H. A. condulet on each side of the 
ways through %-in. (1.86-cm.) conduit. 

In conjunction with this system there is also installed at the 
head of the permanent stocks a Burns water-tight box containing 
a three-wire single-throw 100-amp. knife switch. The box is 



s^ 




.-V>' 



^ 



31 



7"» 



• i-* — — 



.SK8 



r> *- — -> 



xo 




a fc r 6 

<i> !? <n <o 
$ Sf 1 ^ s 



£ G& 



o 

M 

H 

o 

p 

m 

O 
U 






« 

02 
M 

H 

M 
P 

« 

I— I 

O 
o 

M 

H 

X 
o 



CO 

d 

M 



233 



231 ELECTRICAL AIDS TO GREATER PRODUCTION 

mounted at the approximate height of the new vessel's forecastle 
and is intended for temporary wiring when the vessel has 
reached that stage of construction, making its own temporary 
system necessary. The permanent ways in this installation are 
approximately 430 ft. (170 m.) long. 

Lighting of the hull while it is in the first stage of construc- 
tion is of minor consideration, as there is usually plenty of day- 
light before the decking is placed. However, as double bottoms 
and various tanks reach completion temporary lighting by means 
of portable lamps is necessary. At this point of construction 
a specially designed plug board, with provision for ten outlets, 
is placed at the point of greatest demand in the Chester (Pa.) 
Shipbuilding Company's plant. The plug board is as nearly 
foolproof as one can be made, and is fed from a Q. H. A. recep- 
tacle by means of an R. Q. plug and the necessary length of two- 
wire deck cable. These boards are kept in stock, made up, and 
are a part of the standardized electrical equipment of the yard. 

Portable taps made in 50-ft. (15-rti.) lengths and equipped 
with specially designed plugs of very rugged construction are 
taken from the plug boards previously mentioned. The plugs 
are designed to be tapped into one of the outlets of the plug 
board. One end of the '"portable" is attached to a weather- 
proof receptacle equipped with a 60-watt lamp and a locking 
guard. Carbon lamps are preferable for portable work as their 
filaments are more rugged, and, in the writer's opinion, riveters 
are not the gentlest of workmen. 

As the writer's experience has been mostly with vessels con- 
taining six cylindrical tanks, the lighting of such vessels from 
the time that the decking is placed until the permanent electrical 
equipment is in service will be discussed. In the writer's esti- 
mation a tank vessel is one of the worst types to light in a proper 
way temporarily. After considerable experimenting a solution 
to the problems presented was reached. Upon the deck of the 
vessel — or, rather, at the edge of the main trunk deck — a set of 
Xo. 8 weatherproof mains is installed. The mains are mounted 
upon heavy porcelain knobs previously attached to a block about 
2% i n - by 8 in. by 6 in. (6.35 cm. by 20.32 cm. by 15.25 cm.) 
and fastened to the edge of the trunk deck by means of a uni- 
versal girder clamp. The blocks are made in large numbers and 
are kept in stock as part of the standard temporary equipment. 






ILLUMINATION— SELECTION OF EQUIPMENT 235 

The mains are stretched on each side of the vessel and are fed 
from the permanent outlet previously described and installed at 
the head of the ways. This circuit is then again subdivided into 
four sections by means of 60-amp. single-throw knife switches. 
The sections are ordinarily connected but may be isolated to fa- 
cilitate the finding of grounds. Ordinarily the switch at the 
stern is, of course, kept open, but it can be closed in case either 
side of the three-wire system is blown out, thus keeping the loop 
complete until repairs can be made. While the switches previ- 
ously mentioned are part of the standard temporary equipment, 
they are mounted in strongly made wooden boxes of weather- 
proof construction. The ordinary slate base switch is used with 
standard cartridge fuses. 

From the mains the taps are taken for the plug boards and 
for a standardized temporary lighting unit, consisting of an 
X-5423 Benjamin shade, the usual suspension loop, a No. 1388 
guard and a 200- watt nitrogen lamp. This unit is also used in 
the tank vessels. One unit is placed at the top of each cylin- 
drical tank, one in each wing tank, three in the engine room, 
three in the fuel tanks and five in the forecastle, making thirty 
units in all. The units are so arranged electrically that the cir- 
cuit is as nearly balanced as possible. These units are only for 
general illumination. 

For close work the ' ' portables ' ' previously described are relied 
upon, one plug board being installed in each tank, and as the 
work progresses in the other portions o.f the vessel. As the plug 
boards have provisions for ten outlets and the standard "port- 
able" has a length of 50 ft. (15 m.), quite a working radius is 
obtained. The plug boards before mentioned are built in the 
yard and are each equipped with 20-amp. link fuses protected 
by an iron plate. 

In freight vessels the problem is very much simplified as the 
hull is not subdivided as much as in tankers. While the stand- 
ardized mains are used the general arrangement is much sim- 
pler, a single set of heavy mains installed down the center of 
the main deck being sufficient. Since fewer lighting units are 
used only half as many plug boards are required. To locate 
grounds it is, however, advisable to subdivide the mains as in 
the tankers and use ground detectors. The mains are of ample 
size for electrical drilling and reaming. 



236 ELECTRICAL AIDS TO GREATER PRODUCTION 

CHOOSING LIGHTING UNITS FOR INDUSTRIAL 

PLANTS 

Even in times of normal activities manufacturers have found 
that scientific illumination increased the efficiency of their plants 
by making possible (1) greater output, (2) better workman- 
ship, (3) less spoilage, (4) fewer accidents, (5) less sickness, 
(6) reduced labor turnover, and (7) reduced overhead by 
twenty-four-hour utilization of equipment. These benefits are 
of greater importance than ever before, says Davis H. Tuck, 
electrical engineer of the Holophane Glass Company, because 
every manufacturer is confronted with increased costs of mate- 
rials, shortage of labor, and the problem of increasing produc- 
tion without reducing the quality. 

While expert advice is necessary to secure the best illumina- 
tion, owing to the different requirements in different places, ob- 
serving the following suggestions will bring better results than 
not having consulting advice at all. 

Lamp Efficiency. The lamp should give the maximum num- 
ber of lumens (light flux) per watt. 

Life. — The life of a lamp is its economic life and not the 
period which elapses from the time it enters service until it 
fails. The efficiency (lumens per watt) of a lamp falls off with 
use until finally a point is reached where the lamp has become 
so inefficient that it is advisable to throw it away and buy a new 
lamp. The best lamp is, therefore, the cheapest lamp which 
will burn the longest time with the least fall in efficiency (lumens 
per watt) . 

Color of Light. — The light should have a color suitable for the 
work to be performed. 

Reflector Efficiency. The ratio of total lumens from the com- 
bined lamp and reflector to the total lumens from the lamp alone 
should be high. 

Distribution of Light. — It is principally the light in the 0-deg. 
to 60-deg. zone that is of use, therefore the light shown by the 
distribution curve of the reflector should fall as closely within 
these limits as possible. The greater the candlepower of the 
light in the 60-90 deg. zone the greater the glare, and the nearer 
the high candle-power is to the 90-deg. zone the more objection- 
able it is. Some light, to light upper portions of the room, 






ILLUMINATION— SELECTION OF EQUIPMENT 237 

should be contained in the 90 deg. to 180-deg. zone, as it causes 
a strain on the eyes to have too great a contrast between the 
lighting unit and its surroundings. 

Shield Light Source. — The light-producing surface of the 
lamp should be shielded from the eye, as modern light sources 
are too intense for the eye to view with safety. Furthermore, 
the brightness of the lower surface of the reflector should be 
low. 

Maintenance. — The reflector should be durable and the reflect- 
ing surface should not deteriorate with age, heat of the lamp or 
fumes of the shop. It should withstand frequent washing and 
after washing should present a surface equal to the surface 
which existed initially. 

Reducing Shadows. Commenting on the selection of lighting 
units Ward Harrison of the National Lamp Works says: 

In order to take care of the problem of shadows in a satisfac- 
tory manner, it is not only necessary that a sufficient number of 
fixtures be installed, but at all points the light from two or 
more units should overlap. When this plan is followed and the 
spacing between units is made not more than one and one-half 
to one and two-thirds times the mounting height, one can select 
reflectors which give their maximum candlepower directly down- 
ward and still secure practically uniform illumination over the 
working area. If uniformity depended upon one particular 
form of distribution curve, indirect-lighting sj^stems, where the 
ceiling becomes the effective source, would be hopeless from this 
standpoint. 

Hardly any reflector equipped with a clear-bulb lamp would 
give satisfaction for the general illumination of a machine shop 
or any other industrial establishment where polished surfaces 
must be worked upon. 

Again, in almost every factory it is desirable that the light on 
the work should come from sources of large area in order to 
avoid sharp shadows. 

A true comparison of efficiency must be based upon utilization 
factors found by actual test. For a given unit these vary widely 
between small rooms and those of extended floor area. 



238 ELECTRICAL AIDS TO GREATER PRODUCTION 

RATING ARTIFICIAL LIGHTING SYSTEMS 

When making lighting surveys in industrial plants the equip- 
ment will be found in various stages of deterioration. Lamps 
may be dirty and bulbs black; lamps may be used in reflectors 
that are too large or too small for the given size of lamp ; lamps 
may be missing, broken or have their filaments "shorted." Re- 
flectors may be dirty; reflectors may be loose, resting upon the 
bulb for support ; the fixture may be defective owing to worn 
insulation ; the reflector may be broken or missing. All of these 
items decrease the illumination to some degree, and it is impor- 
tant to gain an idea of the percentage decrease in illumination 
which may be ascribed to the combined effect of these factors. 
Obviously it would not be practicable to measure the loss of 
light due to each item for each lighting unit, as this would be 
an enormous task in even a small shop. Therefore an approxi- 
mate system of rating becomes desirable. Such a system, which 
Davis H. Tuck, formerly illuminating engineer for the United 
States Public Health Service, has used in making lighting sur- 
veys in the industrial plants of Wisconsin, will be presented, 
together with comments on the results secured with it. 

The term "efficiency of maintenance" was decided upon as a 
term which could be represented by a percentage figure and 
which would represent both the degree of maintenance that an 
artificial lighting system had received and the percentage of the 
available light that was being received on the working planes. 

In formulating the discounts for various defects in mainte- 
nance it was decided to make the discounts conservative, so that 
a resulting efficiency of maintenance of 100 per cent would rep- 
resent an installation which had received good care but which 
would not necessarily be in perfect condition. Thus a lamp may 
have been in use for 800 hours, and, while not a new lamp, it 
would not be blackened and would be rated at 100 per cent. 

Carbon, metallized and tungsten-filament, mercury-vapor, arc, 
open-flame and mantle lamps become inefficient owing to the fol- 
lowing causes: (1) Continued use; (2) dirt and dust accumu- 
lations on lamps and reflectors; (3) burn-outs and breaks; (4) 
reflectors becoming cracked, broken, loosened or missing, and 
(5) mechanical injury to connections. Various other items of 
deterioration take place so gradually that in many cases they 



ILLUMINATION— SELECTION OF EQUIPMENT 239 

are given no special attention in the practical economy of the 
shop. 

Continued Z7se.— The life of a lamp is not, as is generally sup- 
posed, the elapsed time between its entering into service and 
its burning out. The life of a lamp is given by its manufac- 
turers and is its economic life. Thus when a lamp burns a cer- 
tain number of hours it may be shown that its energy consump- 
tion per light unit has increased to such a degree that it is 
economy to replace it with a new one. 

Dirt and Dust Accumulations on Lamps and Reflectors.- — It 
has been shown by actual measurements that the loss of light due 
to absorption by dust and dirt for average conditions is about 
50 per cent for equipment that has not been cleaned for four 
months; also that a small quantity of dust, so small as hardly 
to be noticeable, will cut down the light by 20 per cent. 

Burn-outs and Breaks. — It is evident that a burn-out or break 
may cut down the light by 100 per cent. Often, however, a 
burn-out or break may be of such a nature that the light source 
does not fail entirely but that the light is greatly diminished. 

Cracked, Broken, Loosened or Missing Reflectors. — The addi- 
tion of a suitable reflector to a lamp generally adds about 50 per 
cent to the light delivered in useful directions. When a re- 
flector is cracked or broken the light from the unit is diminished 
according to the nature of the damage to the reflector. When a 
reflector is loosened from the fixture or bent out of shape the 
distribution is altered and the efficiency of the reflector is low- 
ered. It is evident that when a reflector is missing the light 
that would be gained by its use is totally lost. 

Mechanical Injury to Connections. — The loss of light due to 
mechanical injury to connections will vary with the nature of 
the injury. Often the injury is of such a nature as to cause a 
flickering or intermittent light. It may cause a total failure of 
the light together with all other lights on the same circuit. 

Lighting installations are designed to give desirable initial 
intensities at the work, and it is assumed that the equipment will 
be maintained so as to produce this intensity. From cost con- 
siderations the initial intensity is made as low as possible for 
work to be done efficiently and to insure prevention of eye strain 
and accidents. It is readily seen that when deterioration of the 
lighting equipment sets in the intensity of illumination falls off 



240 ELECTRICAL AIDS TO GREATER PRODUCTION 

and that if this deterioration is not arrested serious efficiency 
losses follow. Often lighting systems are allowed to deteriorate 
to an extreme point, and nothing is done unless complaints 
come in from employees after the lighting facilities throughout 
the shop have become so poor that work has to be temporarily 
discontinued. The production losses from such circumstances 
when added up throughout the year greatly exceed the expense 
of systematic maintenance in advance. 

Even when systematic maintenance is carried out the deteri- 
oration between inspections is marked, and for this reason it is 
desirable to allow a factor of safety when planning lighting in- 
stallations, as is the general practice in other engineering prob- 
lems. The author has frequently found general overhead direct 
and indirect lighting systems which after a trial of six months 
or more have been condemned by the factory management as 
unsatisfactory. In the majority of these cases the trouble lay 
in that the maintenance had been neglected, and in the minority 
it was due to faulty engineering. The stronghold that local 
lighting has in many factories to-day is due to the fact that the 
initial intensity is many times that required for the work at 
hand, and although deterioration is much more rapid for local 
light units than for overhead general units, the factor of safety 
has been made so large that only in extreme cases will the illumi- 
nation fall below requirements. When local lights deteriorate to 
such an extent that they become unsatisfactory the individual 
workman usually makes repairs himself. Thus the trouble is 
not brought to the attention of the management. With over- 
head general lighting, however, the individual workman has no 
control over the units, and when the intensity fails, because of 
lack of maintenance, the job has assumed such proportions that 
the attention of the management is called to the matter. 

In making illumination surveys of shops it was found desir- 
able to note how well the lighting equipment was maintained and 
to arrive at an approximate figure by inspection that would 
denote the degree of maintenance. The term " efficiency of 
maintenance" is used to designate the percentage of the initial 
intensity that a lighting equipment will give, the loss in inten- 
sity being due to the lack of proper maintenance. 

Example of Applying Method. The following table shows 
the method adopted for rating artificial lighting equipment. 



ILLUMINATION— SELECTION OF EQUIPMENT 241 

The efficiency of maintenance in each case represents approxi- 
mately the percentage of light given by the equipment after the 
loss of light due to the corresponding condition is deducted : 

Efficiency of 
Condition Maintenance, 

Per Cent 

Lamp dirty 80 

Lamp very dirty 70 

Lamp blackened, due to aging 80 

Lamp too large or too small for reflector 80 

Lamp missing, broken or having filament "shorted" 50 

Reflector dirty 80 

Reflector very dirty 70 

Reflector cracked or bent 80 

Reflector broken or missing 50 

Connections loose, fuse out or drop cord bare 80 

There follows an example taken from one department of a 
shop recently inspected and referring to general overhead units 
in a tool room : twelve units, lamps dirty, reflectors dirty ; three 
units, lamps dirty, reflectors missing; two units, lamps dirty, 
reflectors very dirty; nine units, lamps very dirty, reflectors 
very dirty; one unit, lamps very dirty, reflectors missing; one 
unit, lamps dirty, reflectors clean; two units, lamps dirty and 
blackened, reflectors dirty. 

To arrive at the efficiency of maintenance for the tool room 
referred to it is necessary to multiply the number of units hav- 
ing the given condition by the values of the efficiency of main- 
tenance for those conditions, expressed as a decimal, and to take 
the weighted mean: 

12 X 0.80 X 0.80 7.68 

3 X 0.80 X 0.50 1.20 . 

2 X 0.80 X 0.70 1.12 

9 X 0.70 X 0.70 4.40 

1 X 0.70 X 0.50 0.35 

1 X 0.80 0.80 

2 X 0.80 X 0.80 X 0.80 1.02 

30 16.57 

(16.57 X 100) -^-30=: 55.2 per cent efficiency of maintenance. 

By measurement with an illuminometer the average illumina- 
tion was increased in the ratio of one to two by bringing the 
efficiency of maintenance up to 100 per cent. By making such 
measurements in a large number of shops, it has been observed 



242 ELECTRICAL AIDS TO GREATER PRODUCTION 

that the efficiency of maintenance of local units is approximately 
one-half that of the overhead general units. 

A department of maintenance of artificial lighting equip- 
ment should be inaugurated in every factory and workshop. 
This maintenance work should be made a part of the electrical 
department, which is in the best position to make periodic in- 
spections of lighting equipment. Reports of inspections, using 
a system similar to the one outlined above, should be made to 
the factory manager and efficiencies of maintenance of 100 per 
cent maintained. The ratings given above are liberal, and effi- 
ciencies of maintenance of 100 per cent are not unreasonable. 

By adopting such a practice a large economic waste caused 
by consumption of energy without adequate return in light pro- 
duction, losses due to decreased production, inferior products, 
accidents and defective eyesight could be avoided. 

ADAPTING 220- VOLT CIRCUITS TO 110-VOLT LAMPS 

Lamps rated at 110 volts or 125 are more efficient than those 
for 220 volts or 250 volts, give a more satisfactory life perform- 
ance and are lower in price than the higher-voltage units, for 
the reason that the higher voltages are nearer the upper limit 




730 Y 



5> 



Motor Load 



230 Y 



5 



230 'K 

ax;: 



230 Y. 

q q q I t 

730 V. 

T T J O O- 

Q 9 9 l<^ 



6 6 6 730 Y 
6 6 6 230 V. 



^ : 6 6 Q 230Y 



Y Y 



■230 Y. 



230 Y 



Lighting Pane! 

C 



V 



Fig. 79 — Undesirable Method of Distribution Often Used for Lighting 

in Industrial Plants 



at which it is possible to manufacture incandescent lamps that 
will be commercially satisfactory. Notwithstanding these facts 
and that there are simple expedients, such as the installation 
of a balancer coil or a motor-generator set, whereby most instal- 
lations where 220-250 volt circuits are used for lighting can be 
changed over so as to use 110-125 volt lamps, there are still a 



w 



© o 



o o 

© cd 
O U 

O 



2 

o c3 

C] cj 

€©■ O 

O 



o u 
O cd 

CO *H 

*> -+J 
1-1 c 
€©• o 



o 



o 




o 


« 


co 


-U 


^ 


fl 




O 




O 




+j 




o 


o 


c3 


o 




CO 


-j-j 


&r 


fl 




o 




U 



+3 
O 

O oS 



feb£» 



£ 




el 


02 


• rH 


be 


<D 





. N 


3 


OQ 


-tJ 




<u 


P-, 


Pi 


g 


S>> 


c3 


-*j 


H-l 


a 




P 




S3 




o 




c$ 




l> 



CO CO 

o o 
o © 


CO 

o 

CO 

o 


»o 
o 
o 

p— 1 


© 

CO 
1—1 


© 
CI 

© 


CO 

CO 

LO 


© 

CO 

© 

CO 


© 

HH 

© 

CO 


© 

CO 
CO 

© 


© © 


d 


d 


© 


d 


© 


© 


© 


© 


i— i i— i 

o © 


F— 1 

Ol 

CO 

q 


CO 

© 

I— 1 


© 

CO 
CO 
rH 


© 


© 

CM 

LO 
LO 


© 

1— 1 
CO 

q 


© 

CO 
Ol 

co 


© 

CO 
CO 

q 




d 


d 


© 


© 


d 


© 


© 


© 


CO CO 
(M CO 

o © 


OS 
CO 

to 

q 


uo 

CO 

o 

1— 1 


© 

CO 

^ch 

I—I 


© 

CO 
CI 


© 

CO 
CO 

LO 


© 
© 

CO 

q 


© 

Ol 

LO 

CO 


© 
© 

OS 


© o 


d 


d 


© 


© 


d 


© 


© 


© 


CO CO 

co ro 
o © 


LO 

CO 

o 


OS 

o 
i—i 


© 

CO 
i— 1 


© 

CO 
CO 


o 

CO' 
LO 


© 

LO 

q 


© 

CO 
CO 


© 

Ol 
CM 

© 


© o 


d 


d 


© 


© 


© 


d 


© 


I—I 


co co 
o © 


CO 

CO 

q 


© 

i— i 
i—i 


© 
CO 

lO 

i—i 


© 

CO 
LO 


© 

co 

© 

CO 


© 

CO 
CO 


© 

CM 

1 — 1 
OS 


© 

CO 

© 


d o 

68- 


d 


© 


© 


d 


d 


© 


© 


!-H 


O © 


i— i 

p — i 

O 


UO 

CO 
1—1 
1—1 


© 
CO 
UO 

I—I 


© 

HH 


© 
oi 

CO 

q 


© 

1— 1 
1 — 1 


© 

GO 
OS 


© 
CO 

© 

I—I 


d d 
e/3- 


d 


© 


© 


d 


d 


d 


© 


I—I 


GO CO 
OS OS 

© © 


q 


lO 

"<cn 
co 

r— 1 


© 

CO 
CO 

1— 1 


© 

00 
OS 


© 

CO 
CO 


© 

b- 


© 

CO 

cs 

OS 


© 

CM 

CO 
I—I 


d d 


d 


© 


© 


d 


© 


© 


© 


I—I 


o © 

lO >o 

q q 


o 

t— i 

CO 

q 


© 
lO 

CO 

1— 1 


© 
© 

CO 

1—1 


© 

© 

uo 


© 
© 

CXI 


© 
© 
i — I 
CO 


© 
© 

CO 

© 


© 
© 

CO 
O] 


d d 


d 


© 


© 


© 


© 


© 


I—I 


1 — 1 


o o 
o o 

CO CO 

© o 


o 
o 
os 
q 


© 

© 

lO 

I— 1 


© 
© 
© 
CO 


© 
© 
© 
cq 


© 
© 
© 

CO 


© 

© 
© 
cs 


© 
© 
© 

CI 


© 
© 
© 


©' d 


d 


© 


© 


d 


d 


©' 


1—1 


1— 1 



Oh 



lO © © © 
CQ t# © © 



& 



O 
-P 
02 

bo 
© 

cfi 

02 

OS 



© © o © © o 

© © O © lO o 

(M M H in n o 



243 



244 ELECTRICAL AIDS TO GREATER PRODUCTION 

great many of the higher- voltage lamps in nse. It is to be as- 
sumed, therefore, that the cost in money or inconvenience is the 
one obstacle that has continued to stand in the way of changing 
these systems over. If this be true, says J. R. Colville of the 
National Lamp Works, the conclusion follows that the greater 
economy effected by adapting 220-250 volt circuits to lamps of 
the 110-125 volt class — a saving that will in general pay in a 
few months the cost of changing the system — is not so generally 
recognized as it might be. 

The difference in cost between lamps of the 110-125 volt class 
and those of the 220-250 volt class when purchased on different 
contract bases, according to schedules in force June 15, 1917, 
are given in Table XXVIII. It may be noted that the difference 







Lighting Panel 

L U L 



Fig. SO — One Method of Adapting 230- volt System to 115-volt Lamps 

in cost ranges from about 4 cents per lamp for the smaller lamps 
when purchased on large contracts to as much as $1.10 when 
the largest lamps are purchased at list price. 

Table XXIX shows the difference in luminous output of corre- 
sponding wattages of lamps of the two voltage classes. It is 
seen from this table that on the average the higher- voltage lamps 
give only about 90 per cent of the light which corresponding 
sizes of the lower-voltage lamps give. Hence for equal illumina- 
tion intensities more wattage is required with the 220-250 volt 
lamps. 

In the design of new installations the number of units which 
may be used advantageously is sometimes closely limited by the 
constructional features of the building. In such cases 220-250 
volt lamps of higher wattage, and frequently the purchase of 
more expensive reflector equipment, are required. On the other 



w 

Hi 
r-3 

«! 

Q 

«1 



H 

*1 
O 

o 

CM 

i 

o 
CM 

CM 

Q 
Eh 

HH 

O 

lO 
CM 
i— l 

I 

O 



Eh 
< 

Q 

> 
i— i 
H 
<1 

PS 

Oh 
O 

o 

I 

XI 
I— I 

XI 

XI 

hi 

pq 



1-3 






73 






PQ 



CO 
rH" 

e 

O 
P 

Eh 

- 

i-i 

H 

03 
«j 
O 



H 

CO -— 

O K! 

,»* co 

Eh & 

> 



m 



© o 

© -h 



o o o 

lO ^ CM 



O O 



o o 

© GO 



o o 
© co 

CO CO 



O O 
© CM 
CM cm' 



^ 



o o 

CO GO 

o" © 



CO lO 

CO H< 

© d 
t— co 

CM CO 

d d 

e/3- €#■ 



b~ CO 
CM CO 

d d 



S ° ° 
cxi o o 

r- ' O H 

go" d" 



s ° ° 

CM O O 
r_l GO \& 



(N 



S ° ° 

n m o 

GO I.- 



© O O 
CM lO o 
i— i i— i © 

© lO 



© O O 
CM lO O 

H CO H 



© o o 

"-H CM CM 

rH Ci l-O 

(M CM 



© 
CO 
CM 



© 
OS 



© 

cs 



CM 

OS 



OS 



U5 

GO 



CO 
CO 



co w o 

CM © © 

i—i os os 



lO lO lO 
OJ N H 
H IQ IQ 



CM CM © 
CM I> 

l-H CO 






CM © © 
CM CM © 
r-H CM i— • 



© 

os. 



© 

OS 



© 

GO 



CO 



o . 



© 

CO 
CM 

►f r co 

H CO g 
rH OJ _£> 

oT of h 

O O H 



Jh H 
Oh Ph 



"£ "£ ^ 

CO GO Oh 

3 3 < 






rH 



?1 

© © s 

"co O 
^ CM >■ 

2 O rH 
g HO ^ 

fl rfl «H 

r^J r^ 



245 






246 ELECTRICAL AIDS TO GREATER PRODUCTION 

hand, if considerable latitude in the location of the units is 
afforded, a greater number of the higher-voltage lamps of a 
given wattage will have to be installed to obtain the same degree 
of illumination as might be obtained with the 110-125 volt 
lamps. This will mean the installation of more outlets, the pur- 
chase of a greater number of reflectors, sockets, etc., and a heav- 
ier maintenance expense. The difference in cost of lamps of 
the two voltages, together with the fact that fewer 110-125 volt 
units are required — that is, the difference in first cost of the 
installation — is often of sufficient magnitude in itself to pay for 
the installation of equipment to provide the lower voltage for 
the lighting circuit. The yearly saving in lamp renewals and 
energy is then pure profit. 

A disadvantage of simply operating two low-voltage lamps in 
series is that failure of one means the outage of both ; thus a 
relatively large area is left without sufficient light and the time 
of several persons may be lost while the defective lamp is being 
located and the replacement made. Obviously in industrial 
plants and shops accident risk under these conditions is increased 
over that when only one lamp is; out. Furthermore, slightly less 
than normal life is to be expected from lamps burning in series, 
since one lamp naturally fails sooner than the other, and when a 
replacement is made the resistance of the old lamp will be higher 
than that of the new one. Hence the new lamp will receive 
slightly less than normal current and will give less than normal 
candlepower, while the old lamp will be forced to carry a some- 
what heavier current than it would normally carry at that period 
of its life and will therefore fail earlier than it otherwise would. 
The better way of obtaining the advantages of the lower- voltage 
lamps is to provide 110-125-volt circuits through balancer coil, 
motor-generator set or other voltage-bisecting device. 

Attention is called to the fact that, in addition to effecting 
maximum lighting economy and obtaining superior service per- 
formance, the user of 110-125 volt lamps receives the benefits 
resulting from the use of a more highly standardized product. 
Lamps of the 220-250 volt range are manufactured primarily to 
supply a small demand which does not justify the stocking of 
quantities of lamps to fill emergency requirements. Further- 
more, improvements are less readily incorporated because of the 
greater manufacturing difficulties presented by high-voltage 



ILLUMINATION— SELECTION OF EQUIPMENT 247 

conditions. Lamps of the 110-125 volt class compose at pres- 
ent approximately 85 per cent of the output of Mazda lamp 
factories, exclusive of miniature lamps, as compared with a fig- 
ure of less than 7 per cent in the case of 220-250 volt lamps. 
For this reason emergencies may be more readily met. 

SOME PHASES OF INDUSTRIAL LIGHTING 

Clothing Factories and Similar Workshops. A government 
report dealing particularly with the women's garment factories 
in New York City brings out the serious fact that over 50 per 
cent of such workshops are inadequately lighted, according to 
the investigations of the United States Health Department. 
Those who are familiar with industrial conditions in New York 
City will, of course, recognize that the situation is probably 
worse there than almost anywhere else, chiefly on account of the 
narrow streets, high buildings and the very common location of 
• clothing workshops in lofts. 

Even when the exposure of the windows is fairly good, the 
areas of the working spaces are often so large that the inner 
portions receive very little light. Of course this situation seri- 
ously aggravates the difficulties of artificial lighting, as it is a 
commonplace of scientific illumination that spaces requiring 
large aid from artificial light are not easy to deal with, and 
that natural and artificial light do not, so to speak, mix well 
from the psychological and possibly the physiological stand- 
point. 

Aside from generally insufficient light, the commonest trouble 
in such factories is serious glare, both directly from the illumi- 
nants and sometimes indirectly from the work as well. This 
trouble comes from the usual cause of bare or insufficiently 
shielded lamps. Comparatively few of those controlling this 
particular industry have as yet seen the economic importance of 
good lighting, and innumerable cases may be found where bare 
gas burners or incandescent lamps are hung low and shine fairly 
in the faces of the workpeople. In not a few other instances 
the lamps originally in the installation may have been tolerably 
well shaded, but later changes have placed, for example, a 
100-cp. tungsten lamp in a shade suitable for a 16-cp. carbon 
lamp, with the result that might be expected. 



248 ELECTRICAL AIDS TO GREATER PRODUCTION 

With the variety of first-class glass and steel reflectors now 
available there is very little excuse for glare, although in rare 
instances the situation of the working spaces is such that ordi- 
nary reflectors prove somewhat inadequate. In this case special 
reflectors may advantageously be used, and we have even seen 
thoroughly good results on a cutting table obtained from the orig- 
inal lamp and reflectors by adding a diffusing skirt deep enough 
to keep direct light out of the operator's eyes. The importance 
in the clothing industry of a good and uniform product turned 
out rapidly is such as to justify considerable expenditure in 
remedying imperfect lighting conditions. These are bad enough 
in dealing with white fabrics, but when dark-colored cloths are 
used the situation becomes much worse. As between white 
goods and dark blues, reds or blacks the illumination required 
for efficient working is somewhat in the ratio of one to four or 
five. For the former between 1 ft.-candle and 2-ft. candles for 
ordinary work seems to be reasonably sufficient; for the latter 
5 to 7 ft-candles will prove to be none too much. 

There is great need for reform in the lighting of clothing 
factories, although now and then a very admirable example may 
be found in which the working conditions as well as the product 
are of the best, but such conditions are unfortunately excep- 
tional. 

Workshop Lighting. The adequate lighting of machine 
shops and foundries is to-day one of the important branches of 
artificial illumination. Owing to the relations existing between 
natural and artificial lighting there is frequent necessity for 
making preparations for the latter in order to secure all-day 
efficiency. Daylight factor — that is, the ratio of the inside to 
the outside illumination — impresses one at first thought as some- 
what indefinite, yet it is the best measure which we have of the 
practical efficiency of the lighting arrangements in a given shop. 
Outside, in full daylight, the illumination may be of the order 
of one or several thousand foot-candles according to the day, 
the hour and the time of year. Within the building there is 
comparative darkness, perhaps 20 to 50 foot-candles in very fa- 
vorable locations, a tenth of this or less in the darker parts of 
the shop. The daylight factor is merely the ratio of the average 
illumination inside to what it would be if walls and roof could be 






ILLUMINATION— SELECTION OF EQUIPMENT 249 

deftly lifted off. The measurement of this factor, involving as 
it does the averaging of interior conditions, is a somewhat labo- 
rious matter. Possibly it could be considerably facilitated by 
the use of an actinometric method ; but however measured it does 
express the broad facts, and the startling thing about it is the 
very small value of the factor usually found, very rarely 10 per 
cent, not infrequently down to 1 per cent or even a tenth of 
this small quantity. In other words, in full daylight one may 
easily have only one or two foot-candles at certain points within 
the building. Hence it happens that on dark and cloudy days 
and during the weak light of winter one may often have within 
a workshop far less light than is necessary for efficient operation. 

Now, it seems to be a well-established fact that with modern 
gas-filled lamps well arranged, particularly where off-peak rates 
can be obtained, the cost of artificial light is less than the over- 
head on extra space required to increase output, so that in more 
cases than one would at first suppose artificial light may be eco- 
nomical where only a day shift is in operation. A fairly strong 
and well-distributed light can be secured at a very moderate 
expense. The intensities which seem to be necessary generally 
are from 2 to 4 foot-candles, with for special purposes excur- 
sions to considerably higher figures. The method most effective 
is general overhead illumination giving the nearest approxima- 
tion to the distribution of light obtained by day. 

The most difficult practical problem is that which often arises 
in the case of large working spaces of which portions are inade- 
quately lighted. The mixture of daylight and artificial light is 
not altogether agreeable, and perhaps only for psychological 
reasons there is often a feeling that the artificial light is inade- 
quate when it is really quite as strong as that previously ob- 
tained by day. The contrast between light near the windows 
and light within the interior of a shop lighted only from the 
sides is of course striking. Shops with monitor roofs and plenty 
of light from above fare better, but the general indication is 
that an artificial lighting equipment powerful enough to give a 
night shift opportunity to work to its highest efficiency is an 
extremely good investment. 



250 ELECTRICAL AIDS TO GREATER PRODUCTION 

COST OF FACTORY LIGHTING 

Within limits, a few lighting units form a cheaper equip- 
ment than do many, this being subject to the varying conditions 
imposed by the necessities of distribution and the grade of illu- 
mination required. In making or analyzing any estimates of 
this kind the construction costs will, of course, vary enormously, 
depending on the class of building, the uses to which it is put, 
the costs at the moment of material and labor and a good many 
other factors, so that one may say at the start that it is difficult 
to find two cases exactly comparable. The best that can be done 
is to analyze each case so thoroughly that one can accurately 
deduce its relation to other cases. A great deal of this cost 
reckoning is a matter of bookkeeping; in one example the cost 
per outlet was carried clear back to the transformer and switch- 
board equipment. Such an all-inclusive scheme may be at times 
justifiable, but is likely to involve considerable errors and cer- 
tainly is not a ready basis for the comparison of lighting instal- 
lations as to initial cost. 

What is much more important is the figure for a complete 
installation of wiring, lamps and accessories up to the switch- 
board. In some cases further segregation in the costs compared 
is necessary, as when the new system is operated from old mains. 
One cannot in the long run do much more than furnish general 
data for which rough estimates of cost can be made, just as the 
complete solution of the illumination problem in any given 
factory cannot wholly be trusted to general average but must 
involve factors based on local circumstances. 

UPKEEP OF INDUSTRIAL LIGHTING SYSTEMS 

It is well known to illuminating engineers that many an 
installation thoroughly satisfactory at first proves inefficient in 
the long run. Part of the difference may be charged up per- 
haps to the psychological factor which makes the human mind 
discontented with its wonted conditions, but there is in addi- 
tion a very real depreciation in service due to lack of care and 
the inevitable incidence of dirt. According to data which has 
been accumulated on a typical factory case it pays, from the 
standpoint of efficiency versus cost of upkeep, to clean lamps 



ILLUMINATION— SELECTION OF EQUIPMENT 251 

and reflectors about every two weeks. Where dirt is more than 
usually severe the interval should be shorter than this; where 
less severe it may be somewhat longer. From a practical stand- 
point the fact which stands out conspicously is that if the clean 
lamp in its reflector is operating on the basis of 1 watt per 
candle as short a period as three weeks without cleaning may 
reduce the lamp to a rating of about 2 watts per candle. If it 
were suggested to the factory manager at the present time to 
use lamps having so low a rating he would be astonished and 
incensed ; yet from ignorance of the facts losses of this magni- 
tude may be going on right under his nose all the year round. 

Lighting a Loom Room for Overtime Operation. Being con- 
fronted with the now common problem of overtime operation, 
the Vogt Manufacturing Company recently had to rearrange its 
looms and improve the illumination. In one part of the factory 
a direct-lighting system had been tried out. This consisted of 
three 60-watt lamps with extensive reflectors hung about 4 ft. 
(1.2 m.) above the bar of the loom and equally spaced along it. 
The rear of the loom was illuminated by a 60-watt lamp. This 
direct system was found to cause shadows and did not give 
satisfaction. 

In the new loom room the looms are illuminated by 200-watt 
type C lamps in Druid No. 3031 11-in. (28-cm.) semi-indirect 
glass fixtures. The ceiling and walls were covered with two 
coats of Rice's "mill white." To provide for portable lights a 
drop was hung over each loom within easy reach of the operator 
so that he could plug in an extension cord equipped with a 
trouble lamp. However, when the semi-indirect system was in- 
stalled it was found that the intensity of light and the lack of 
shadows made a trouble lamp superfluous. 

It is interesting .to note that this semi-indirect system of illu- 
mination cost less to install than any other system and gave bet- 
ter results, according to F. C. Taylor, who contributed this in- 
formation. 

Lighting Crane Areas. The lighting of crane areas in ma- 
chine shops and foundries often presents a difficult problem. 
On account of the necessary clearance for the crane, it is cus- 
tomary to install the lighting units close to the roof or even with 
the bottom of the trusses. Owing to the height, either 750-watt 
or 1000-watt lamps are necessary. In nearly all cases it will be 



, 



252 ELECTRICAL AIDS TO GREATER PRODUCTION 

found that better results can be obtained by the use of angle 
reflectors when placed about 14 ft. to 15 ft. (4.3 m. to 4.6 m.) 
above the floor and between the columns and arranged to deflect 
light rays toward the center of the crane-way. - This arrange- 
ment will not only cause better distribution, but will do so at an 
appreciable saving in energy. 

The suggested method of lighting will be found very adapt- 
able to ordnance buildings, where the rifling machinery is gen- 
erally placed in the crane area and very close to the columns. 
It will be found that porcelain-enameled reflectors will give bet- 
ter results and at the same time will require less cleaning. Tests 
show that the width of the area as well as the height of the unit 
will determine the shape of the angle reflector best adapted for 
each individual case. Care must be exercised in designing such 
a lighting system so that no dark areas result along the floor 
on the center line of the building, says Leo Dalkart. 

How to Avoid Moving Factory Wiring. Quite frequently in 
industries doing light manufacturing it becomes necessary to 
move the tables, benches or machines at which the workers stand 
or sit. If the scheme of illumination includes a combination of 
general and localized lighting, it then becomes necessary to move 
the localized lighting equipment to accommodate the new loca- 
tion of the tables or machines, which adds considerably to the 
expense of making the change. In some of the manufacturing 
industries operated by Marshall Field & Company of Chicago a 
large part of this expense has been eliminated by attaching the 
conduit, wiring and lighting fixtures to the tables instead of to 
the ceiling above the tables. With this scheme the only change 
in wiring that needs to be made when the tables are moved is 
the one connection from the overhead conduits to the conduit 
above the table. 



CHAPTER V 
ELECTRIC FURNACES, WELDING, ETC. 

ELECTRIC FURNACE FOR NON-FERROUS 
METALLURGY 

Certain fundamental principles, upon which the success of 
electric brass melting directly depends, have hardly received, at 
least in public, the consideration which they deserve, so they will 
be discussed in this paper by H. M. St. John of the Common- 
wealth Edison Company, Chicago. In discussing them particu- 
lar attention will be called to the bearing which they have upon 
electric furnace design and development. 

In 1914 it was estimated by Gillett * that there were in the 
United States at least 3600 plants engaged to some extent in 
melting brass and bronze. It was further estimated that the 
value of the metal annually melted by these plants was in the 
neighborhood of $120,000,000, and that of this total the value of 
the metal lost beyond recovery during the melting operation 
was not less than $3,000,000. When one considers the extensive 
use of brass and bronze in warfare and the enormous industrial 
expansion along metallurgical lines which has taken place in this 
country since 1914, it should be evident that corresponding fig- 
ures for the present time are much larger. Even if the total 
amount of metal melted annually were no greater now than then, 
the increase in market value of the metals concerned would of 
itself nearly double the value of the metal produced. The 
avoidance of waste in melting, which was even then considered 
important, therefore becomes particularly so at this time. 

As has long been known, it is theoretically possible to eliminate 
much of this loss by the use of electric melting, particularly in 
the case of yellow brass and other alloys high in zinc. Most of 
the electric furnace development in the copper-alloy field has 

i H. W. Gillett, "Brass-Furnace Practice in the United States," Bureau 
of Mines Bulletin No. 13, p. 9 (1914). 

253 



254 ELECTRICAL AIDS TO GREATER PRODUCTION 

been carried out with this end in view. Metallurgically speak- 
ing, the problem is not a simple one and progress has been 
rather slow. Important advances have been made since 1914, 
however, and the present outlook is rather optimistic. 

Two widely different types of electric furnace are now on the 
market and in commercial use for melting yellow brass. One is 
highly efficient but limited in its use to a portion of the field 
only; the other is less efficient but otherwise more widely appli- 
cable. At least one other type of furnace has been experimen- 
tally successful and is reported as about to enter the commer- 
cial field. Two or three additional types are being actively de- 
veloped and give some promise of eventual success. 

So far as yellow brass is concerned, it cannot be said that 
an entirely satisfactory furnace has yet been produced, but the 
field has been partly covered, and the prospects for further 
advancement in the art are good. 

Previous to the war the use of electric furnaces for melting 
copper alloys did not seem feasible except in cases where a large 
metal saving helped to counterbalance the higher cost of electric 
heat. Under present conditions the high cost and poor quality 
of crucibles, the high cost and shortage of important metals, the 
high cost and scarcity of labor and the insistent demand for a 
high rate of production at any cost are factors which combine 
to make electric melting profitable in many cases where it would 
previously have been unprofitable. Whether electric furnace in- 
stallations which owe their existence to these peculiar conditions 
will continue to show a profit when normal conditions once more 
prevail is still an open question. No one can say when condi- 
tions will again become normal, or, for that matter, what sort of 
conditions will be considered normal in the future. Much will 
depend upon the progress made in furnace design and in oper- 
ating methods during the continued existence of the economic 
conditions which at present make possible the electric melting 
of copper alloys containing little or no zinc. The necessary 
progress can only be made by the combined efforts of such indi- 
viduals and companies as are now profiting, and expect to profit 
in the future, from the increased use of electric furnaces. 

Advantages of Electric Melting. Electric heat is expensive 
at best, and although it can be applied much more efficiently 
than heat derived from fuel, especially at high temperatures, it 



ELECTRIC FURNACES, WELDING, ETC. 255 

cannot profitably be employed except in cases where its use 
makes possible substantial savings of one kind or another to 
offset its added cost. The advantages which may naturally be 
expected to accrue from electric melting, as compared with melt- 
ing in fuel-fired furnaces, are roughly as follows : 

Metal Saving. — The saving of metal otherwise unavoidably 
lost is the principal economic advantage which the electric fur- 
nace is required to show in the melting of copper alloys, par- 
ticularly in melting yellow brass. It has been completely dem- 
onstrated that such a saving can be made in the electric furnace 
by virtue of the fact that the furnace chamber can be tightly 
closed during the melting period and a neutral or reducing 
atmosphere maintained. As will be shown later on, it does not 
follow that every electric furnace is capable of a favorable per- 
formance in this respect. Conditions resulting from the war 
have greatly accentuated certain other advantages of electric 
furnace operation. 

Improved Quality. — It has been found in most cases that a 
more uniform quality of metal can be produced in the electric 
furnace than in fuel-fired furnaces operating under similar con- 
ditions and that it is easier to produce an alloy of closely speci- 
fied composition. In general, these advantages can be accepted 
as inherent in properly conducted electric furnace operation, re- 
sulting from the greatly reduced loss of volatile metals and from 
the elimination of contaminating combustion gases. So far as 
copper alloys are concerned, it is still undecided whether or not 
a higher quality of metal can be produced in the electric furnace 
as compared with the best of fuel-fired practice. It is beyond 
question, however, that high quality can be achieved more easily 
and with greater certainty. The successful electric furnace 
must be at least as satisfactory in these respects as the best 
fuel-fired furnace. 

Exact Temperature Control. — The production of perfect cast- 
ings, with the least possible number of defective pieces, depends 
in large degree upon the use of metal at a temperature which 
conforms closly with that known to be most favorable for the 
work in hand. The electric furnace lends itself readily to exact 
temperature control, which is an important advantage. 

Increased Production. — In general, the speed of melting is 
greater in electric furnaces than in fuel-fired furnaces, because 



256 ELECTRICAL AIDS TO GREATER PRODUCTION 

of the higher operating temperature and greater efficiency ob- 
tained. Furthermore, larger units can usually be employed 
than when fuel-fired furnaces are used. 

Elimination of Crucible Cost. — The cost of crucibles is an item 
of considerable magnitude even in normal times. Under pres- 
ent conditions this cost is very high. Electric furnaces, which 
require no crucibles, therefore eliminate this expense. Large 
fuel-fired furnaces effect the same saving, but from a metal- 
lurgical point of view are seldom as satisfactory as fuel-fired 
crucible furnaces. Electric crucible furnaces deserve little con- 
sideration at the present time. 

Incidental Savings. — The operation of large units results in 
an economy of floor space and labor, and increased production is 
attended by decreased overhead and interest charges per ton of 
metal produced. 

Better Working Co)iditio)is. — More favorable conditions for 
the workmen, tending to increase their efficiency as well as their 
comfort, result when excessive heat, noise and fumes are elimi- 
nated. Properly selected and correctly operated electric fur- 
naces are almost ideal in this respect. In installations where 
the reverse is true the trouble is due to the use of an unsuitable 
furnace, or to careless operation, or to both of these as contrib- 
uting causes. 

It should not be understood that these advantages necessarily 
follow from the use of any electric furnace which may happen 
to be selected. The furnace must be of suitable type, properly 
designed and correctly used. A misapplied electric furnace may 
prove worse in almost every respect than the fuel-fired furnace 
which it replaces. 

First consideration must always be given to metallurgical re- 
quirements. Steel may be heated as rapidly as desired during 
the melting operation, provided that it is not exposed to con- 
taminating elements during the process, but with copper alloys 
the case is quite otherwise. Copper is somewhat volatile and 
oxidizes much more readily than steel when in the molten state. 
Lead is also quite volatile, more so than copper, and oxidizes 
very easily. Zinc is exceedingly volatile at molten brass tem- 
peratures. All copper alloys must be treated carefully during 
the melting process in order that losses of metal by oxidation 
and volatilization may be kept at a minimum. 



ELECTRIC FURNACES, WELDING, ETC. 257 

Requirements of Electric Melting. Yellow brass for thin 
castings must be poured at a temperature not far below its boil- 
ing point in order that the metal may be sufficiently fluid. At 
this temperature zinc, which comprises 30 to 35 per cent of the 
alloy, has a tendency to vaporize rapidly. So long as the metal 
is contained in a tightly closed furnace chamber, which can 
easily be done in the electric furnace, this tendency is counter- 
balanced by the vapor pressure of the metal which has already 
been vaporized and with which the furnace atmosphere is satu- 
rated. When the furnace is opened for pouring the metal or for 
any other purpose the vapor pressure is released and additional 
zinc will escape from the metal without restraint. If the heat- 
ing has been perfectly uniform and all portions of the melt are 
at approximately the same temperature, the loss of zinc which 
ensues will constitute an unavoidable minimum. If the heating 
has not been uniform, some portions of the melt will be at a tem- 
perature higher than the desired pouring temperature, and such 
portions will lose zinc at a higher rate. If the lack of tempera- 
ture uniformity is very great, the loss which occurs after the 
furnace is opened and during pouring will be decidedly exces- 
sive. If the metal is seriously overheated during melting the 
high vapor pressure formed within the furnace will force con- 
siderable quantities of zinc vapor through crevices in the furnace 
structure. In some cases it may be practically impossible to 
keep the furnace chamber closed, even to a reasonable degree. 
Under such conditions the zinc losses are likely to be quite as 
serious as in fuel-fired crucible furnaces, or even more so. 

What is true of yellow brass poured at a temperature near its 
boiling point is also true, although in less degree, of yellow 
brass poured at lower temperatures and of other copper alloys. 
The lower the percentage of volatile metal the more easily the 
alloy will withstand uneven heating, but it can be accepted as 
an axiom of copper alloy melting that heat must be applied to 
the metal as uniformly as possible, whether the alloy under 
treatment is brass, bronze or some one of the less common alloys. 
If the application of heat in the furnace lacks uniformity to a 
serious degree, an excessive loss can only be prevented by some 
method of stirring the metal, and this stirring must be effected 
within the furnace, but without opening the furnace doors. 

The metal as poured from the furnace must be uniform in 



258 ELECTRICAL AIDS TO GREATER PRODUCTION 

composition, with its various constituent metals thoroughly well 
mixed and alloyed. In some cases a rigidly specified composi- 
tion must be closely met. The finished casting or ingot must 
be of a quality at least as good, with respect to strength, free- 
dom from cracks, blow-holes, etc., as that obtainable from fuel- 
fired crucible furnaces. 

Since electric heat is more costly than that derived directly 
from fuel, it is important that the thermal efficiency of the 
electric furnace should be as high as can be obtained consist- 
ently with other requirements. A high thermal efficiency in 
electric melting, unless heat is generated in the metal itself, re- 
quires a high temperature heat source, placed as close as may 
be to the metal, under conditions which offer the least possible 
opposition to the flow of heat from the source to the metal. At 
the same time the walls of the furnace must be sufficiently 
thick and of high-heat-insulating quality in order that heat may 
not be dissipated uselessly from the outer walls. 

In some types of furnaces these requirements are directly 
opposed to the metallurgical requirements already considered. 
In such cases thermal efficiency must be sacrificed to as great a 
degree as may be necessary in order to satisfy the metallurgical 
requirements. The highest efficiency consistent with good met- 
allurgical results should be maintained; any higher efficiency is 
false economy. Of course, other things being equal, the more 
efficient type of furnace will meet with greater success. 

The electric furnace, to reap the full benefit of its economic 
possibilities, must operate in large units and must not use cru- 
cibles. The higher its speed of melting the better, so long as 
speed is not detrimental to metallurgical results. 

The electrical characteristics of the furnace must be such as 
to make it a desirable load for the central-station company or 
the factory power plant. Its power factor must not be abnor- 
mally low and its power fluctuations must not be so violent as 
to endanger transformers and other electrical equipment or to 
interfere with satisfactory service to other customers of the 
central-station company that may be connected with the same 
power line. 

It hardly seems necessary to add that the successful electric 
furnace must be sturdy and reliable, quite as capable of per- 
forming its function, day in and day out, under regular oper- 



ELECTRIC FURNACES, WELDING, ETC. 259 

ating conditions, as are the best types of fuel-fired furnaces. 
The furnace and its adjustments should be as simple as possible, 
although with a large electric furnace it is permissible, and 
nearly always desirable, to use a higher grade of operator than 
would be employed to tend fuel-fired crucible furnaces. 

A great variety of electric furnace types have been proposed 
and tried out for melting brass. It is hardly an exaggeration 
to say that every known method of applying electric heat to a 
metal has been utilized by one or another of the various designs 
which have reached at least an advanced experimental stage. 
Some of these types have been eliminated as inherently unsuited 
for the purpose; some have been abandoned because of difficul- 
ties which may eventually be overcome by other investigators; 
others, partially successful, have apparently reached the height 
of their development; still others seem to possess greater possi- 
bilities of ultimate success than have yet been demonstrated. 

TYPES OF ELECTRIC FURNACES FOR NON-FERROUS 

METALLURGY 

The obvious method of reaching a high thermal efficiency 
without overheating an alloy is to generate heat in the metal 
itself by the passage of an electric current through it — either 
by a direct resistance furnace, in which electrical contact with 
the metal is made through electrodes, or by means of an induc- 
tion furnace, in which case the metal forms a complete circuit 
for the flow of an induced electric current, without the use of 
electrodes. In either case it is practically necessary to establish 
the circuit through molten metal previously melted in some other 
furnace. 

Direct-Resistance Furnaces. The "pinch-effect" direct- 
resistance furnace was the first type in which this principle was 
utilized. Virtually all of the heat is generated in the molten 
metal temporarily occupying channels or tubes. The main por- 
tion of the metal, occupying the furnace chamber above, is 
heated by contact with the hot metal, and solid metal added to 
the bath is melted by the same means. 

The stirring action of the moving streams of metal is vigorous, 
and the temperature of the main portion of the bath rises 
uniformly. There is no difficulty in restraining the vaporization 



260 ELECTRICAL AIDS TO GREATER PRODUCTION 

of zinc, and, in fact, it may be said that the metallurgical re- 
quirements of any single alloy are almost perfectly fulfilled. 

Generation of heat in the metal itself, where its presence is 
desired, is theoretically ideal from the standpoint of efficiency, 
since no part of the furnace is any hotter than the metal, and 
wall losses are reduced to a minimum. With this type of fur- 
nace, however, the massive metallic electrodes require a consider- 
able water cooling. Consequently a large quantity of heat es- 
capes from the furnace, and the thermal efficiency is much lower 
than it would otherwise be. Considerable difficulty has also 
been experienced in constructing satisfactory transformers for 
use with the extremely low voltages and high currents required. 
So far as is known to the writer this furnace is not now used ex- 
tensively.. 

Induction Furnace. The next step in the development of 
electric furnaces was the application of a similar principle to 
the induction furnace. In this the use of electrodes and trouble- 
some transformers is avoided, since the furnace serves as its 
own transformer. The generation of heat takes place as before 
in the resistor channels, and the same vigorous circulation of 
metal results. "Whether this action is due primarily to the pinch 
phenomena or to a motor effect resulting from the now of 
current through the continuous molten resistor is open to ques- 
tion. It is difficult to tell where one phenomenon leaves off 
and the other begins. 

The thermal efficiency of the induction-type furnace, operat- 
ing, as it does, without electrodes, is very high, probably higher 
than that of any other electric furnace ever tried out for copper- 
alloy work. Its metallurgical characteristics are also excellent,. 
It offers a perfectly steady, uniform load at a power factor 
which is satisfactory, at least in the relatively small sizes so 
far built, the largest requiring a 60-kw. input and pouring 
600 lb. of metal per heat. In larger sizes there might be trouble 
with low power factor, as is so frequently the case with large 
induction furnaces. 

The induction furnace is in commercial use and is said to be 
giving satisfactory results. It has, however, pronounced limi- 
tations which are partly inherent in its design and partly reme- 
diable. Its small size is one disadvantage, but it is probable that 
somewhat larger sizes can be successfully built. So far it has 



ELECTRIC FURNACES, WELDING, ETC. 261 

not been found practicable to use the furnace with alloys high in 
lead, because that metal has a tendency to penetrate minute 
cracks in the lining' of the resistor channels, causing short 
circuits. The remedy for this is the development of a lining 
especially suited for use with lead. 

The more serious limitations of the furnace are its lack of 
flexibility in changing from one alloy to another and the prac- 
tical necessity of operating it continuously, never allowing 
the furnace to cool oftener than once a week. The length and 
cross-section of the resistor channels are especially designed to 
accord with the electrical resistance — in the molten state — of 
the alloy which is to be used. These same resistor channels 
cannot be employed with another alloy of widely different resist- 
ance, which, accordingly, requires the installation of new chan- 
nels of properly modified design. In changing from one alloy 
to another, even if the resistance is approximately the same, it 
is necessary to pour the furnace clean and start with a molten 
charge of the new alloy, melted in another furnace. 

The linings of the resistor channels stand up very well under 
continuous use but deteriorate rapidly under the daily heating 
and cooling of ten-hour-day operation. This can be obviated 
by maintaining over night sufficient power to keep the channels 
filled with molten metal, which, of course, results in some ad- 
dition to the cost of operation. 

The limitations mentioned tend to prevent the use of this fur- 
nace in commercial foundries, which melt a wide variety of 
alloys and do not work nights, but form no bar to its use in 
yellow-brass rolling mills, to the purposes of which it seems 
well suited. 

There has been proposed a new design of induction furnace 
which would not be subject to the foregoing limitations. In this 
type a spark gap and an arrangement of condensers connected 
in series and in parallel are used in the primary circuit of the 
furnace, which operates at about 10,000 volts and some 15,000 
to 20,000 cycles. The secondary of the furnace consists of a 
crucible or melting chamber with electrically conducting walls. 
The metal within the crucible also carries part of the second- 
ary current, to a minor degree when it is first charged in the 
form of solid pieces, to a much greater degree when it becomes 
molten. The primary circuit is arrariged around the melting 



262 ELECTRICAL AIDS TO GREATER PRODUCTION 

chamber and is separated from it by suitable refractory and 
heat-insulating walls. The furnace is, in a sense, an eddy- 
current rather than an induction furnace, since no iron cores 
are used and the metal itself, lying in a circular pool, completely 
short-circuits what, in an induction furnace, would be called the 
secondar3 r circuit. This unique arrangement is made possible 
by the exceedingly high frequency used. 

According to last accounts, this furnace had been built only 
in very small sizes, capable of pouring not more than 45 lb. 
(20.4 kg.) of metal per heat. There is no apparent reason why 
the metallurgical characteristics should not be good, and the 
construction of the metal-containing portion of the furnace is 
desirably simple. It is obviously unnecessary to use molten 
metal in starting the furnace. Any alloy or even non-conduct- 
ing material, such as glass, can be melted without changing the 
furnace design. The furnace is suitable for intermittent opera- 
tion and need not be kept hot overnight. 

Arc Furnaces. Next to the methods already described the 
most direct way of applying heat to the metal is by means of a 
heat source outside but in direct contact with the bath. The 
direct-arc furnace is the only type which utilizes this principle. 

The application of direct-arc furnaces to copper alloy melting 
has been rather limited. One or two furnaces designed for steel 
melting have been tried, but no new type of direct-arc furnace 
has been developed for this specific purpose. No furnace of this 
general type has ever succeeded in satisfactorily melting yellow 
brass or other copper alloys containing an appreciable percent- 
age of zinc. The high-temperature heat source in direct contact 
with the bath overheats the metal in its immediate vicinity and 
always causes excessive loss of zinc. 

With copper alloys containing no zinc conditions are some- 
what different, since lack of uniformity in heating is less likely 
to result in serious loss. In a direct-arc furnace of small size 
it has been found possible to melt a copper alloy containing as 
much as 15 to 20 per cent lead with less loss than is commonly 
the case with the same alloy in fuel-fired crucible furnaces. In 
larger furnaces the greatly increased rate of heat input supplies 
heat to the metal in the neighborhood of the arch more rapidly 
than it can be conducted away to more distant portions. As a 
result the surface of the metal becomes overheated while other 



ELECTRIC FURNACES, WELDING, ETC. 263 

parts of the bath are still much below the desired temperature. 

Advantage of Direct-Arc Furnace. The direct-arc furnace 
has the advantage of simplicity and high thermal efficiency. Its 
design has been more highly developed and perfected than that 
of most other electric furnace types. Since it is so widely 
used in the steel industry, several reliable and readily available 
furnace designs are on the market. It is very doubtful, how- 
ever, if any direct-arc furnace deserves wide application for 
melting copper alloys. Its use is limited to only a few of the 
common alloys, and, if large units are employed, the metal loss, 
even with these alloys, is likely to be serious. Small units are 
more satisfactory in this respect, but are subject to the disadvan- 
tages of lower efficiency, higher fixed charges and higher operat- 
ing costs per ton of metal produced. 

Such direct-arc furnaces as are now in use in this field — and 
there are a few — hold their place by virtue of their simplicity, 
their elimination of crucible cost and their high rate of produc- 
tion, at a time when these qualities are at a premium. 

The intensity of heat application to the metal is lessened some- 
what by using an arc between two or more independent elec- 
trodes above the bath, heating the latter by direct radiation. 
The arc does not come in direct contact with the metal, and the 
latter forms no part of the electric circuit. It is apparent that 
in this type of furnace the surface of the metal is not so seri- 
ously overheated as in the direct-arc furnace, but such overheat- 
ing as exists is, nevertheless, too severe to permit the use of 
such furnaces in melting yellow brass. The indirect-arc fur- 
naces can be used economically with alloys containing 5 to 10 
per cent of zinc, possibly as high as 20 per cent, but certainly 
not for higher values. 

Indirect-Arc Furnace. The design of the indirect-arc fur- 
nace is invariably somewhat more complicated than is the case 
with the direct-arc furnace, and its thermal efficiency is not so 
high, but in the melting of copper alloys it can be economically 
used in large units and seems to be in general a more satisfactory 
tool for the purpose. 

Several indirect-arc furnaces are now in use in this country 
for melting copper alloys which contain small percentages of 
zinc or none at all. In a new type of indirect-arc furnace the 
metal, as soon as it becomes molten, is agitated by rocking, the 



264 ELECTRICAL AIDS TO. GREATER PRODUCTION 

furnace mechanically, in order to avoid overheating of the sur- 
face layer. In this way non-uniformity of heating is largely 
rectified, and it is possible that alloys high in zinc can be melted 
without excessive loss. The furnace has received a comprehen- 
sive commercial test, the results of which have been published by 
the Bureau of Mines, Washington, D. C. This type gives con- 
siderable promise of success and should be applicable to a wide 
field of alloy melting. 

Indirect-Resistance Furnaces. Resistance furnaces which do 
not utilize the metal itself as an electric resistor may be grouped 
in three classes — (1) those which radiate heat directly to the 
metal, similar in principle to the indirect-arc furnace; (2) those 
which radiate heat to the furnace roof and thence to the metal 
by reflection and secondary radiation; (3) those which deliver 
heat to the metal by conduction through a refractory wall. 

Heating by direct radiation is the most desirable of the three 
from the standpoint of efficiency. For this purpose it is prac- 
tically necessary to support the resistor above the bath in some 
manner, and this has never been done successfully in furnaces 
of any size. In small furnaces it has been possible to utilize 
this principle and to melt brass satisfactorily without over- 
heating the surface of the metal to an undesirable degree, since, 
as compared with an arc, the resistor has a large area and oper- 
ates at a much lower temperature. At the same melting speed 
the application of heat to the metal is more uniform but the 
efficiency is somewhat less. 

This type of furnace is applicable to the melting of yellow 
brass but is not in commercial use because of the mechanical 
difficulties involved in its construction. The possibility of its 
eventual use depends upon the development of a resistor mate- 
rial which is at once highly refractory, homogeneous, mechani- 
cally strong at high temperatures and possessed of a fairly high 
electrical resistance at the working temperature of the furnace. 

The second type of indirect resistance furnace named ranks 
next in order of thermal efficiency. In this design a refractory 
wall separates the resistor from the metal, although not neces- 
sarily in contact with the metal, and the major portion of the 
heat is radiated from the resistor to the furnace roof, the latter 
acting as a secondary heat source which reflects and radiates 
part of the heat which it receives to the bath beneath it. The 



ELECTRIC FURNACES, WELDING, ETC. 265 

heat has to travel a rather long path, and much of it is lost by 
the wayside. As a result the furnace is. not so efficient in prin- 
ciple as those previously discussed. In order to stimulate a rea- 
sonably rapid flow of heat the resistor element must be much 
hotter than the roof, and the roof, in turn, much hotter than the 
metal. Thus the possibility of a high rate of production de- 
pends upon the use of a resistor capable of operating at a tem- 
perature very much above that of the metal, even at the pouring 
point. The furnace roof must be exceedingly refractory, and 
the brickwork in the immediate neighborhood of the resistor must 
be even more refractory than the roof. 

This furnace, in common with other indirect resistance fur- 
naces, has another disadvantage, somewhat minor in character 
but worth considering, which does not exist with direct-resistance 
furnaces, nor to any great degree with arc furnaces. The heat 
storage of the furnace is large and the stored heat is at a higher 
temperature than that of the metal. Consequently, the tempera- 
ture of the metal will continue to increase after power has been 
shut off so that the metal must be poured promptly when it has 
reached the desired pouring temperature in order to avoid over- 
heating. 

This is the only form of indirect resistance furnace which has 
been used commercially for melting copper alloys. In its pres- 
ent form it is simple, reliable, easy to operate and can be used 
for practically any alloy, with either intermittent or continuous 
operation. Its metallurgical characteristics are excellent, with 
the single exception that it is somewhat difficult to secure thor- 
ough mixing. It is also especially suitable for melting alloys 
high in zinc. However, its production rate is not rapid and it 
is not so efficient as the types of furnaces already described. 

A similar type of furnace exists in which a combination of arcs 
and resistance elements is utilized, all radiating heat to the 
furnace roof, which, as in the furnace just described, serves as a 
secondary heat source. The use of arcs makes possible a consid- 
erably higher power input, more rapid melting and probably a 
slightly more favorable efficiency, provided that a sufficiently 
refractory roof is used. A very high efficiency cannot, however, 
be expected from this type of furnace. Certain difficulties in 
furnace design have been encountered which have so far post- 
poned the commercial use of this furnace. It has been under 



266 ELECTRICAL AIDS TO GREATER PRODUCTION 

test for some time, but the results obtained have not yet been 
made public. 

The least efficient method of transferring heat from its source 
to the metal is to force it through a refractory wall, even though 
this wall be that of a clay-graphite crucible, a mixture which has 
a fairly high heat conductivity. Theoretically, the least unde- 
sirable arrangement under these conditions is to inclose the re- 
sistor in the refractory wall or to use the wall itself as a resistor. 
In the latter case the wall must be separated from the metal by 
an insulating layer to prevent short-circuiting. It is not an 
easy matter to make this insulation permanent, so this factor has 
been a serious source of difficulty. A resistor inclosed in a re- 
fractory wall tends to reach excessively high internal tempera- 
tures, and no material, satisfactory in other respects, has yet 
been found which will not destroy itself under these conditions. 
Another troublesome difficulty results from the ease with which 
most resistor materials unite chemically with the furnace refrac- 
tories at high temperatures, thereby destroying both themselves 
and the refractories. Some two or three furnace types have 
been designed to make use of this principle, but they have been 
collectively unsuccessful. At present there is no real activity 
along this line. 

Crucible Furnace Low in Thermal Efficiency. Finally, it is 
possible to melt brass in a crucible by means of resistor elements 
which surround but do not touch the crucible. Perhaps the 
most perfect results, from a metallurgical standpoint, can be 
obtained in this manner, but the thermal efficiency is at a mini- 
mum, and in any case the electric crucible furnace lacks most 
of the secondary advantages upon which the electric brass-melt- 
ing furnace must depend in part for its successful use. In 
cases where perfection of metallurgical results is by far the most 
important consideration it is possible that an electrical crucible 
furnace can be employed profitably, but, so far as is known to 
the writer, no commercial installation of this kind exists. 

So far as thermal efficiency is concerned, the crucible furnace 
takes its place at the bottom of the list. Its energy consumption 
per ton of metal produced is about three times that of the in- 
duction furnace. One or two attempts have been made to im- 
prove the efficiency but owing to the facts just stated its devel- 
opment has been discontinued. 



ELECTRIC FURNACES, WELDING, ETC. 267 

Present Progress and Development. The development of 
electric furnaces for non-ferrous metallurgy has been studied by 
Dwight D. Miller, formerly with the Society for Electrical De- 
velopment, who says that the furnaces which have been designed 
and are now under experimentation include the Gillett furnace 
(indirect-arc type), patent assigned to the government, Depart- 
ment of the Interior, Bureau of Mines; the Conley furnace 
(molded-resistor type), controlled by Florance & Hampton, 1270 
Broadway, New York; the Thomson-FitzGerald furnace (rever- 
beratory resistance type), controlled by John Thomson, '253 
Broadway, New York; the Northrup furnace (induction type 
without iron core), controlled by the Ajax Metal Company, 
Philadelphia, and the Hering "pinch-effect" furnace, controlled 
by Carl Hering, Philadelphia, although an option is held by the 
Ajax Metal Company for handling brass in the furnace. Other 
furnaces are under experimentation, but the companies inter- 
ested in them are averse to giving any information thereon. 

The Gillett furnace, invented by Dr. H. W. Gillett, is an in- 
direct-arc furnace so designed as to bring about a violent agita- 
tion of the charge by a rocking motion. Instead of rotating the 
furnace through a complete revolution which would involve dif- 
ficulties in keeping the metal out of the joint between the door 
and the door opening and in making bus contacts to the elec- 
trodes, it appears simpler to rock the furnace back and forth so 
that the molten charge just fails to reach the door at either end 
of the rocking angle. Accurate temperature control is very easy 
in the rocking furnace, since the walls are no hotter than the 
metals and there is no heating up of the sides from hotter roof 
and walls. After cutting off the arc the temperature falls very 
slowly, about 2 or 3 deg. C. per minute. By running the arc a 
minute or so every ten or fifteen minutes, the charge can be held 
at pouring temperature for an indefinite period. Where auto- 
matic electrode control is used one man can probably attend to 
two furnaces. 

The Conley furnace, invented by William H. Hampton, is a 
resistance furnace of the molded-resistor type, in that the charge 
is melted in an open graphite crucible which closes the secondary 
circuit. The voltage is applied directly to the sides of the cruci- 
ble, the latter being inclosed in an iron-plate casing packed with 
Kieselguhr. Hand control is used for varying the voltage in 



268 ELECTRICAL AIDS TO GREATER PRODUCTION 

the primary circuit and consequently in the secondary circuit. 
The furnace is capable of melting 100 lb. (45.3 kg.) of copper 
with 12 kw.-hr. input. The power factor is practically unity — 
98 to 99 per cent. 

The Thomson-FitzGerald furnace, invented jointly by John 
Thomson and Francis A. J. FitzGerald, is a resistance furnace 
of the reverberatory type, the heating effect being produced by 
radiation from especially formed resistors and reflection from the 
walls and roof of the furnace inclosure. The apparatus, which 
is designed for the purification of spelter containing metals, has 
been tested chiefly for the fuming of impure zinc. While the 
furnace has been successful in producing extremely pure zinc, 
no performance data are available for publication. 

The Northrup furnace, invented by Prof. Edward P. North- 
rup, has been under experimentation for the last year, during 
which time some data have been obtained. The furnace is an 
absolutely new departure in furnace design and principle of 
operation. It employs oscillatory current at very high voltage, 
the oscillation being produced by discharges from a condenser 
and being conducted to a series of closed coils which are mounted 
concentrically on cylindrical crucibles and insulated from each 
other. A 20-kw. Northrup furnace will melt 45 lb. (20.4 kg.) 
of brass scrap in thirty-five minutes, starting from the cold. 
Temperatures as high as 1600 deg. C. are readily obtained. The 
furnace is admirably adapted to make melts in vacuum and is 
now being used for melting both glass and electrically conduct- 
ing materials. 

"So far as the writer is aware," said Mr. Miller, "nothing is 
being done at present with the Hering 'pinch-effect' furnace, 
which has been fully described in the technical press." 

Furnaces in Commercial Use. The furnaces that are in ac- 
tual commercial practice for handling copper-zinc alloys include 
the Ajax Wyatt furnace, controlled by the Ajax Metal Com- 
pany, Philadelphia; the Foley furnace, controlled by Charles B. 
Foley, Inc., 170 Broadway, New York; the Baity furnace (rever- 
beratory resistance type), controlled by the Electric Furnace 
Company of America, Alliance, Ohio ; the Rennerfelt furnace 
(indirect-arc type), represented by Hamilton & Hansel, 17 Bat- 
try Place, New York; the Snyder furnace (direct-arc type), con- 
trolled by the Industrial Electric Furnace Company, 53 West 



ELECTRIC FURNACES, WELDING, ETC. 269 

Jackson Boulevard, Chicago, and the Hoskins furnace (resist- 
ance type), controlled by the Hoskins Manufacturing Company, 
Detroit, Mich. 

The William A. Rogers Company, Ltd., which uses Baily fur- 
naces, states that virtually no metal losses are involved when 
handling silver using two crucibles holding approximately 500 
oz. (14 kg.) each, that the metal appears more homogeneous, 
and that a better melt is obtained. The first heat takes about 
one hour and thirty minutes, while the others take approxi- 
mately one hour, the average total time for charging, melting 
and pouring being approximately one hour and seven minutes. 
The company can get about eight heats (of two crucibles each) 
in a day of ten hours. 

The pouring temperature is around 2200 deg. Fahr. (1209 
deg. C), although no pyrometer is used, the temperature being 
judged by the color. The furnaces operate with a constant in- 
put of 30 kw., which figures out 960 kw.-hr. per ton. The elec- 
trodes in the silver furnace are replaced once every three months, 
but as they use the butts left over from the annealing furnaces 
this renewal costs them practically nothing. 

The Otis Elevator Company has two Baily annealing furnaces 
of 300 kw. and 150 kw. capacity for treating steel and brass 
castings. About the only trouble experienced has been an occa- 
sional cracking of the resistor troughs, thereby necessitating 
patching. These two furnaces are energized by one three-phase 
transformer, the large furnace operating two-phase and the 
smaller one single-phase. The troughs are in series, thus pro- 
ducing an even balanced load. 

The castings treated vary from 3 lb. (1.4 kg.) up to 7000 lb. 
(3175 kg.) each. The larger furnace can handled a charge up 
to 12,000 lb. (5443 kg.) of metal, while 7500 lb. (3402 kg.) can 
be charged in the small furnace. The metal is treated at a tem- 
perature ranging from 1500 deg. Fahr. to 1850 deg. Fahr. (815 
deg. C. to 1026 deg. C.) and heated for from sixteen to twenty 
hours. Starting with a furnace temperature of approximately 
750 deg. Fahr. (398 deg. C.) and running up to an annealing 
temperature of 1600 deg. Fahr. (871 deg. C), at which time the 
current was shut off, the cost per ton was approximately $7, the 
total time the power was on being nineteen and three-quarter 
hours. 



270 ELECTRICAL AIDS TO GREATER PRODUCTION 

At the Lumen Bearing Company, Buffalo, copper, lumen 
metal, phosphor and manganese bronze are being handled in 
Baity furnaces. The charge is 600 lb. (272.2 kgf.), consisting of 
scrap and ingots. Short test runs on both lumen metal and 
phosphor bronze under far from ideal conditions resulted in a 
consumption of 12 kw.-hr. for lumen and 22 kw.-hr. for phosphor 
bronze per 100 lb. (0.49 kw.-hr. per kg.). The company states, 
however, that as soon as it gets to running ten hours per day 
six days in the week it expects to reduce these figures to 10 
kw.-hr. and 17.5 kw.-hr. respectively, basing this expectation on 
making the hardener used with lumen metal, and which forms 
28 per cent of the melt, separately in a crucible. 

The lumen metal is poured from 1250 to 1600 deg. Fahr. 
(754 to 871 deg. C), the phosphor bronze at approximately 
2200 deg. Fahr. (1209 deg. C). The heats average about one 
hour so that eight or nine heats can be made in a ten-hour day 
according to conditions. The metal loss will vary from 2^2 to 
3V2 per cent for the lumen metal, the test on the phosphor 
bronze showing 2 per cent. 

With the idea of getting the hearth in good condition a melt 
of copper amounting to 1512 lb. (685 kg.) was run just previous 
to the test run on phosphor bronze. This was held for four 
hours and twenty minutes with a consumption of 24.8 kw.-hr. 
per 100 lb. (5.5 kw.-hr. per kg.), starting with the furnace hot. 
The charging was done in nine separate lots extending over 
three hours while six pours were made, ranging from 2000 deg. 
to 2100 deg. Fahr. (1094 deg. to 1150 deg. C.) in forty minutes. 
Under these conditions the figures given should not be considered 
as a true • indication of the performance of the furnace when 
handling copper. It is possible to charge manganese bronze 
immediately after a lumen heat since the zinc which might be 
left in the furnace would have no injurious effect on the man- 
ganese bronze. 

Of the two furnaces installed one has been in operation for 
six months and the other for two months. During this time 
there has been only one renewal of the bottom, costing about 
$50, with some slight patching in addition. The second furnace, 
however, is not run every day. 

Regarding savings the statement is made that with coke cost- 
ing $4 and crucibles 4 cents there is a saving made by using 



ELECTRIC FURNACES, WELDING, ETC. 271 

electricity at 0.75 cent per kilowatt-hour, which is virtually what 
is paid. In addition, the labor of carrying the coke and ashes 
is eliminated together with the space for their storage. 

The Hoskins Manufacturing Company gives the following 
information regarding the performance of several of its fur- 
naces: "The smaller, holding one crucible, usually gives four 
to five heats of 23 lb. (10.4 kg.) each per day, but we have no 
power figures on it. It is lined with 4!/2 in. (11.4-cm.) magne- 
site back of the resistor and 4i/2-m. (11.4-cm.) firebrick back of 
this. This brick lining has to be rebuilt every six to eight weeks 
and is patched every Saturday. The larger furnace, taking two 
crucibles, is lined with 41^-in. (11.4-cm.) carborundum bricks 
just back of the resistor, with 3-in. (7.6-cm.) powdered silica 
back of this, and finally with 2y 2 -m. (6.4-cm) Kieselguhr brick 
back of this. This furnace has to be rebuilt every three to four 
months, and it is patched every Saturday. In it the current is 
turned on every morning at 4.30, increased at 7 a. m. to prob- 
ably 40 kw., when charging begins, and later run at 50 kw. to 
60 kw. Five heats of 23 lb. (10.4 kg.) each are usually turned 
out per day, the first at about 11 a. m. and the others every one 
and a third to one and a half hours, using for the day from 
450 kw.-hr. to 525 kw.-hr. These alloys are poured at about 
2900 deg. Fahr. (1589 deg. C.)." 

Results of Tests on Brass. The results of five tests on yellow 
brass (65 to 85) showed an average of 49 kw.-hr. per 100 lb. 
(1 kw.-hr. per kg.), pouring at 1950 deg. Fahr. (1063 deg. C). 
The melt was made in a 70-lb. (31.8-kg.) crucible in an FC 
furnace. The total time per heat outside of the first, which took 
two and a half hours, was approximately one hour. Eight tests 
on red brass showed an average of 36.5 kw.-hr. per 100 lb. (8 
kw.-hr. per kg.), pouring at about 2150 deg. to 2175 deg. Fahr. 
(1170 deg. to 1190 deg. C). The first and average heat took the 
same time as for yellow brass. No metal loss was given in either 
case. 

"The only installation of Snyder furnaces handling non- 
ferrous metals of which I am aware," said Mr. Miller, "is that 
at the Chicago Bearing Metal Company. The power factor is 
in the neighborhood of 60 per cent." The furnaces have a 
capacity of about 2000 lb. (907 kg.) of metal 'per heat, and the 
average power consumption is not over 300 kw.-hr. per ton (333 



272 ELECTRICAL AIDS TO GREATER PRODUCTION 

kw.-hr. per t. ) . They operate twenty-four hours per day, Sun- 
days excepted, and handle a heavily leaded bronze such as is 
used for railway car and locomotive bearings. The composition 
of the metal is approximately 75 per cent copper and the balance 
is lead, tin and miscellaneous impurities in that order of im- 
portance, the lead running about 15 per cent. The metal is 
poured at approximately 2100 deg. Fahr. (1148 deg. C), and 
while the metal loss is fairly high, mostly lead and some copper, 
about $12,000 net is saved per month by doing away with the 
crucibles, since these two furnaces replace forty to fifty coke 
and oil-fired furnaces. The high metal loss follows naturally 
from the use of a direct-arc furnace, since it is bound to pro- 
duce a superheated top layer in the bath. 

Rennerfelt furnaces of 1/3 ton (302 kg.) and 1200 lb. (544 
kg.) capacity are in operation at the Gerline Brass Foundry 
Company's plant, Kalamazoo, Mich., and at the Philadelphia 
Mint respectively. At the mint some French and Italian coins 
composed of almost pure nickel have been handled, the lining 
standing up very well although the melt was at a high tempera- 
ture. They use a ganister bottom with silica brick linings. 
This furnace should give a very good account of itself in han- 
dling alloys of this nature. 

In the furnace at the Gerline brass foundry red brass, enamel 
tank (half red and half yellow brass with not over 22 per cent 
zinc content) and monel metal have been handled, but not much 
success was attained with yellow brass ingots. The furnaces 
could not handle yellow brass borings at all. This was only to 
be expected since neither the direct nor the indirect arc type 
of furnace is suited for handling alloys containing metals which 
volatize at comparatively low temperature unless some method is 
provided for overcoming the superheated top layer. 

While too much reliance should not be placed on operating 
figures obtained as the result of experimental runs, and this 
remark will apply to those previously given, still as an indica- 
tion of what may be expected the following results are given : 

Out of four heats making monel-metal castings, three showed 
no metal loss and the fourth heat a loss of 3.3 per cent. The 
average of the actual melting time was three hours and forty- 
eight minutes, with a kilowatt-hour consumption of approxi- 
mately 1300 kw.-hr. per ton (1444 kw.-hr. per t.). The average 



ELECTRIC FURNACES, WELDING, ETC. 273 

charge was 549 lb. (249 kg.) with an average electrode consump- 
tion of 5 lb. per ton (2.5 kg. per t.). 

The results of seven heats making enamel-tank castings under 
fair operating conditions showed an average metal loss of 3% 
per cent, with an average of actual melting time of one hour 
and forty-eight minutes. The average kilowatt-hour consump- 
tion was 537 kw.-hr. per ton, while the electrode consumption 
was 2.8 lb. per ton (1.4 kg. per t.). The average charge was 
580 lb. (263 kg.). 

Ten heats were selected from those making red brass castings 
as representing fair working conditions. The results show the 
average charge to be 532 lb. (241 kg.), with an average of actual 
melting time of one hour and fourteen minutes. The average 
kilowatt-hour consumption was 437 kw.-hr. per ton (485 kw.-hr. 
per t.) with an electrode consumption of 2.8 lb. per ton (1.4 
kg. per t.). 

It should be noted that the kilowatt-hours required for making 
red brass castings are less than those for enamel tank, which 
simply goes to show that experimental figures cannot be relied 
on for commercial practice. In order to obtain figures of value 
full and complete data as to all conditions should be recorded. 

Regarding the whole question of labor savings, it can be 
stated that arrangements have already been worked out whereby 
pouring castings or blanks direct from the furnace can be ac- 
complished. In the case of small furnaces these can be picked 
up bodily and brought to the pouring floor, while in the case of 
the larger-sized furnaces the molds can be arranged to pass 
under the spout by means of a conveyor system. 

It should also be noted that very little use is made of the 
pyrometer for accurate recording of temperature of melt. 
"This, in my opinion," said Mr. Miller, "is a mistake and much 
to be regretted, since the primary object of the use of the elec- 
tric furnace is to reduce metal losses by more accurate control 
and to keep full and complete daily records which can be used 
in determining the best practice and eliminating preventable 
losses. ' ' 



274 ELECTRICAL AIDS TO GREATER PRODUCTION 

THE PROPERTIES AND USE OF FURNACE 
ELECTRODES 

In an issue of the London Electrical Review appeared an inter- 
esting article on the properties and utilization of electric furnace 
electrodes. The article dwells on the rate of consumption of 
electrodes, methods of protecting and cooling, means of attach- 
ing conductors, and arrangements for controlling the electrodes. 
Extracts therefrom are given in the following paragraphs: 

Consumption of electrodes is due primarily to the following 
causes : Dissociation by current ; the working voltage may be 
either too high or too low; chemical combination of the elec- 
trodes with oxygen; solution of the carbon in the metal, and 
direct oxidation by atmospheric oxygen. The electrodes should 
not be burned too close to the terminal clamp nor should they 
be rejected as new electrodes may cost £17 ($82.50) per ton 
and stumps may be worth only 32s. ($7.35) per ton as raw ma- 
terials for fresh electrodes. The scrap A^alue is thus only 10 
per cent of the value new. To utilize the stumps arrangements 
can be made for fastening them to the new electrodes, using 
screw connections or lap- joined construction. 

The most effective protection for electrodes consists of a 
sheath of incombustible material. Mixtures which have been 
proposed for this purpose are retort coke and sodium silicate ; 
lime and limestone with carbon, and potassium or sodium silicate 
with chalk. These mixtures applied cold form a covering which 
is a good resistant to heat. Other protective coatings used are 
asbestos wool with silicates, milk of white clay, and silundum. 
The last is an amorphous compound resembling carborundum. 
It is refractory, incombustible, and, being a compound of carbon 
and silicon, it is useful for protecting electrodes in ferro-silicon 
furnaces. An iron netting may be used to support a paste of 
sodium silicate and clay or of gaolin and asbestos. Sometimes 
granular material unaffected by oxidizing gases is embedded in 
the surface of the electrode. Quartz, alumina or carborundum 
may be used, according to the nature of the products made in 
the furnace. Rigid envelopes of asbestos board or sheet iron 
have also their uses, though care is required to prevent air cir- 
culating between electrode and sheath, which then forms a draft 
chimney and intensifies the damage. 



ELECTRIC FURNACES, WELDING, ETC. 275 

In this connection Ch. Louis recommends that the electrode 
be protected by an agglomerate of magnesia or dolomite, 3 cm. 
to 5 cm. in thickness, inside a jacket of 1-mm. sheet iron. The 
agglomerate is heated for mixing and contains 6 to 7 per cent 
of pitch and 5 to 8 per cent of tar. Adherence on the electrode 
is increased by chipping its surface and painting it with tar. 
The sheath being held in place by an external mold, the agglom- 
erate is packed tightly between it and the electrode. The mold 
is then withdrawn, and a joint is made at the top between 
sheath and electrode by a paste of silicate or refractory earth. 
It is not essential to rebake an electrode thus protected. 

The Grin process is to embed the electrodes in a carbon agglom- 
erate. With this end in view the electrodes are formed of sev- 
eral cores (say, eight or ten), and the agglomerate is a mixture 
of coke or ground electrode stumps with pitch or tar. The 
agglomerate forms simply a mechanical bond between the elec- 
trodes. It is not traversed by any considerable fraction of the 
current and is, therefore, at a much lower temperature than the 
cores and is less exposed to oxidation. Its protective action 
endures beyond the point in the furnace at which iron sheathing 
would be melted away. 

It is evident that a protective coating of any sort carries its 
impurities into the manufactured product, and for this reason 
it is sometimes better to do without the coating and simply 
modify the shape of the electrodes. 

The rate of electrode consumption referred to unit weight of 
product manufactured varies widely with the product concerned 
and with the type of furnace employed. For instance, in the 
manufacture of 25 per cent ferro-silicon the electrode consump- 
tion is about 3 mm. per hour, increasing to 4 mm. when a 58 
per cent silicon alloy is made. Manganese-silicon alloys involve 
a mean consumption of 3 mm. and calcium carbide of 2 mm. 
per hour. All these figures refer to covered furnaces charged 
continuously in which consumption is always a minimum. 

In aluminum manufacture the electrode acts not only as a 
current conductor but also as a comburent, and its consump- 
tion is generally proportional to the quantity of metal pro- 
duced — say, 700 gm. per kg. (1500 lb. per ton) of metal pro- 
duced. 

In steel furnaces of direct-production type, with electrodes 



Lb. 


Remarks 


I51/2 to 22 


Charged cold 


25 




24.8 




38.5 




5.9 


Fluid charge 



276 ELECTRICAL AIDS TO GREATER PRODUCTION 

about 2 m. long, the consumption varies with the process. The 
following table shows the net weight of electrodes burned effec- 
tively in various works : 

Electrode Consumption per 
Ton of Steel 
Furnace • Kg. 

Stassano, Turin 7 to 10 

Girod, Urgine 11.4 

Chapelet, Allevard 11.3 

Heroult, LePraz 17.5 

Lindenburg, Eemscheid 2.68 

Allowing for stumps of utilization and starting directly from 
ore, the average net consumption of electrodes is now 4 kg. to 
5 kg. (8% lb. to 11 lb.) per ton of steel. In some cases elec- 
trodes have lasted for 1200 working hours, corresponding to 
more than six weeks of continuous operation. 

Electrode Terminals and Cooling Arrangements. The man- 
ner in which electrodes are supported while being left free for 
up and down adjustment at will and the manner in which con- 
nection is made to the electric supply mains play an important 
part in the maintenance and durability of electrodes. Bad fit- 
ting may cause the electrode to become red hot at places, and 
this in turn leads to breakage or excessive combustion. The 
damage is cumulative because the resistance of carbon decreases 
with increasing temperature ; hence current passes by prefer- 
ence through the overheated parts, aggravating their state and 
exposing them to yet more rapid depreciation. 

There are several methods available for the attachment of 
carriers to electrodes, but the two types at present in use are 
clamp connections and central connections. Cooling may be 
secured in all cases by a water basin near the connection or by 
a trough of water surrounding the electrode and provided, if 
necessary, with radiating ribs or wings. 

Electrode Cooling. — Haakon Styri suggests a simple arrange- 
ment for cooling electric-furnace electrodes by water. The cool- 
ing water comes through the armored hose to a distributing box, 
fastened on the outside of the columns for the electrode holders. 
Only three pipes go out from the distributing box — one to each 
electrode — each of which is furnished with a regulating valve. 
Where the pipe passes the roof ring a piece of rubber hose is 
inserted for insulation and connected with a union to the pipe 






ELECTRIC FURNACES, WELDING, ETC. 277 

which goes to the cooling ring. The return pipe from the cool- 
ing ring is connected with a union to the rubber hose, which is 
sufficiently long to allow for total electrode movement and some 
surplus to prevent kink. This rubber hose is again, by means 
of a union, fastened to the pipe leading to the electrode holder, 
and the return pipe from this is, by means of union and rubber 
hose, connected to the downflow pipe, which is fastened to the 
electrode carriage. From this pipe the armored rubber hose 
leads to the common waste-water box. 

Leads for Furnaces. In cases where the common distance 
between leads is relatively great, considerable can be gained by 
making the leads of two concentric tubes, says Arvid Lindstrom 



CT ISO J S Amp 



C.T 120/5 Amp. 

L ^^ TOr> 1 1 ' 1 7c? Graphic 

1 ' > Wattmeter 

and Relays 




To Furnace 



To Hand Control 



Fig. 81 — Proper Connections eor Balancing and Regulating Three- 
phase Currents in Steel Furnace 



in the Teknisk Tidskrift. The inductance as well as the increase 
in the resistance will thus be a minimum. In those parts of the 
circuit, on the other hand, where each pole has a separate path 
the use of a single group of laminated bars for each lead would, 
in general, seem unsuitable. This is especially true where large 
cross-sections are involved. As near as possible to the place 
where the leads separate, each conductor should be divided into 
two groups, placed sufficiently far apart with respect to the 
length. With not too great a current, each of these groups may 
consist of a single bar whose thickness should not exceed 15 mm. 
to 20 mm. If the current is great, so that for practical reasons 
a total thickness of the bars for each group of more than 20 mm. 
would have to be used, tubes should be used instead of bars. 



278 ELECTRICAL AIDS TO GREATER PRODUCTION 

Otherwise the arrangements should be as stated previously. In 
general, a greater diameter of the tube (and consequently a less 
thickness of the walls) as well as a greater distance between the 
groups will give a better result in regard to the inductance as 
well as to the increased resistance. 



HEAT TREATING BY ELECTRIC MEANS 

The field of the resistance-type furnace is mainly in opera- 
tions requiring temperature between 400 deg. and 1650 deg. 
Fahr. (200 deg. and 900 deg. C.) and includes such work as 
annealing and heat treatment of steel and other metals and 
melting of non-ferrous metals, especially those with a strong 
affinity for oxygen. Some data on Baily furnaces follow: 

One furnace with a 20-in. by 12-ft. (50.8 cm. by 3.7 m.) 
hearth used for annealing brass and silverware blanks handles 
1 ton (0.9 t.) of blanks per hour with an energy input of about 
200 kw. A motor-driven pusher mechanism pushes pans car- 
rying the blanks into the furnaces and discharges other pans 
on the other side into a quenching bath at the end of each an- 
nealing period. Another furnace of the same general type, but 
with its pusher mechanism automatically controlled by clock- 
actuated -relays, is handling steel motor-car parts. Its hearth is 
26 in. (66 cm.) wide by 12.5 ft. (3.8 m.) long. It is heating 
800 lb. (282 kg.) of steel to 1650 deg. Fahr. per hour with an 
electrical input of 130 kw. A third size of this general type 
has a hearth 4 ft. (1.2 m.) wide by 20 ft. (6.1 m.) long. It is 
heating 1.5 tons (1.4 t.) of steel to 1650 deg. Fahr. per hour with 
an electrical rating of 360 kw. The largest size of this type in 
operation has a hearth 7 ft. (2.1 m.) wide and 20 ft. (6.1 m.) 
long and handles 3 tons (2.7 t.) of steel to 1650 deg. Fahr. per 
hour. It is rated at 660 kw. Equipments of this character, 
when automatically controlled by a contact-making pyrometer, 
reduce the human element to a minimum and lessen the chance 
for error in treatment. One man loads the pans. Drawbar 
knuckles and motor-car parts are among the products now being 
treated in these furnaces. 

Another and somewhat similar type of furnace is known as 
the car type. With this type parts loaded on cars are pushed 
into the furnaces, treated and pushed out. Cast-steel parts for 



ELECTRIC FURNACES, WELDING, ETC. 279 

motor-car construction, locomotives and car axles, aluminum, 
copper, brass and gun castings and forgings are treated in these 
car-type furnaces. Among the sizes of this type now in opera- 
tion are those with hearths 4 ft. (1.2 m.) wide and 10 ft. (3m.) 
long, with a capacity of 0.5 tons (0.45 t.) per hour and a rating 
of 150 kw., and those larger sizes with 6-ft. (1.8-m.) by 18-ft. 
(5.5-m.) hearths with a capacity of 1 ton (0.9 t.) of steel per 
hour and a rating of 300 kw. 

A new type of furnace that is just being put into operation 
for annealing steel and copper is the recuperative car type. t It 
is arranged to accommodate two lines of cars passing through 
the furnace in opposite directions, so that the hot outgoing cars 
give up some of their heat to the cold cars on the way in. This 
furnace, which is 22 ft. (6.7 m.) wide and 19 ft. (5.8 m.) long, 
is rated at 600 kw. It will heat 150 tons (143 t.) of steel to 
1500 deg. Fahr. or 350 tons (317 t.) of copper or brass to 1200 
deg. Fahr. (649 deg. C.) in twenty-four hours. No covers are 
required to keep the metal from scaling. 

Another new type of special furnace is one built for reduc- 
tion of tungsten ores. It is also of the car type. The cars with 
their contents are, however, moved continuously through the 
heated furnace, which is gas-tight. After being fully heated the 
cars are pushed into a long discharge hood to cool slowly. The 
furnace is built in one size only. It is 10 ft. (3m.) wide, 50 
ft. (15.2 m.) long, and has a capacity equivalent to annealing 
0.5 ton (0.45 t.) of steel to 1650 deg. Fahr. (900 deg. C.) in one 
hour. It is rated at 150 kw. 



PYROMETER SYSTEM FOR ANNEALING FURNACES 

An indicating and recording pyrometer system that is giving 
complete satisfaction to both the furnace operator and the metal- 
lurgist was installed some time ago by T. W. Poppe in connection 
with a battery of six annealing and hardening furnaces. Six 
indicating pyrometers with the auxiliary equipment are installed 
on the checkers' bench; the recording pyrometers are situated 
in the metallurgist 's laboratory and signaling lamps are mounted 
over each furnace to notify the attendant when the temperatures 
of the furnace are high, low or correct. Three thermocouples 
are installed in each furnace so that the central and end tern- 



280 ELECTRICAL AIDS TO GREATER PRODUCTION 

peratures can be observed, and so the operator can determine 
which fnel valve to operate to keep the temperature correct. To 
avoid the use of too many pyrometers and still not hinder the 
observation of temperatures, the thermocouples are connected in 
groups of six to three circular switches, which in turn are con- 
nected with double-pole, double-throw switches. 

A small hole is provided in each furnace where the tempera- 
ture is desired and the thermocouple centrally attached to a 
tripod the feet of which rest upon the top of the furnace. What 
might be called a stuffing box is provided to seal the space be- 
tween the thermocouple and the furnace casing, the construc- 
tion, (c) in the accompanying illustration, being such that the 
thermocouple can be raised or lowered by adjusting the tripod 
attachment. This arrangement also makes it easy to remove the 
thermocouples for renewal or inspection. To prevent the leads 
of the thermocouples carbonizing, owing to heat escaping through 
the holes in the top of the furnace, long enough thermocouples 
are used so that their upper ends can be bent at an angle of 90 
deg., bringing the cold ends 1 ft. (0.3 m.) from the middle of 
the furnace, where the circuits run into conduits leading to the 
checker's bench and metallurgist's office. 

All of the wires, which have asbestos insulation, are installed 
in iron conduit. The checker's bench being centrally situated, 
a 2-in. (5-cm.) conduit was installed from it to a pull box placed 
between the third and fourth furnaces. From this point to the 
second and fifth furnaces 1%-in. (3.8-cm.) conduit is used and 
reduced to 1 in. (2.54 cm.) where it extends- to the first and 
sixth furnaces. From the main conduit %-in. (1.9-cm.) con- 
duit extends above the furnaces to points over the thermocouples, 
where %-in. (1.9-cm.) conduit tees equipped with porcelain 
bushings are provided. One-and-one-half-inch (3.8-cm.) conduit 
is used between checker's bench and the metallurgist's laboratory. 



ELECTRIC WELDING 

Great economy has been effected in the Rock Island Railway 
system, saj T s E. Wanamaker, by means of electric welding devices 
which perform a variety of services, such as cutting plates and 



ELECTRIC FURNACES, WELDING, ETC. 281 

holes, the welding together of sheets, welding of tubes to the back 
flue sheets and repairing holes in fire boxes of locomotives. The 
"metal electrode" method of welding is employed, using a soft 
steel wire or other metal as the negative. Direct-current energy 
at 20 volts is furnished by a number of portable motor-generator 
sets which are applicable to the considerable varieties of work. 
The detailed results of six months' operation, based on the ex- 
penditure of $40,000 for electrical welding outfits, show that 
85.7 per cent of the cost of welding by older methods was saved 
by the new system and that the electrical system shows a> sav- 
ing of 28.5 per cent over the gas method. On the basis of 
results obtained thus far, Mr. Wanamaker calculates the rate of 
saving to be $200,000 per year. Of this, $136,000 is a direct 
saving in the performance of the work and $64,000 represents 
increased service of engines due to shorter time for repairs. 
By extending the use of the electric welding operation over the 
whole Rock Island system Mr. Wanamaker estimates a possible 
yearly saving of $1,000,000. 



COMPARATIVE CHARACTERISTICS OF ARC 

WELDERS 

The characteristics of the different types of direct-current 
welders are so well known because of their years of use that 
there is not much use in going into their characteristics except 
in a very general way. The direct-current machines are of two 
general classes — those which get their regulating properties from 
resistance and those which have the regulating properties in- 
herent in the machine. Both are successful when properly de- 
signed and both are in use in large numbers. The machine 
which eliminates resistance is somewhat simpler as far as control 
is concerned and uses considerably less power. Where a multi- 
plicity of operators is required the first cost of the apparatus 
is larger than with the resistance type. Which one is best suited 
to the work depends entirely on conditions, and for that reason 
both are used to a very considerable extent. 

Characteristics of Alternating- Current Arc Welder. The 
alternating-current arc welder, however, is of more recent de- 



282 ELECTRICAL AIDS TO GREATER PRODUCTION 

velopment and its characteristics are not so well known. In 
discussing the claims made by the sellers of this type of appa- 
ratus, J. F. Lincoln points out that as is the case with all ap- 
paratus, this type of welder has some points which are very 
valuable and others which are not. A consideration of the facts 
in the case as applied to each job will generally decide for the 
buyer which type should be used. The claims made for the 
alternating-current machine are the following: (1) No mov- 
ing parts; (2) no commutator with its consequent trouble; 
(3) possible portability by hand; (4) high efficiency, and (5) 
low cost. 

The first two claims are borne out except fer the fact that in 
order to reduce the size of the welder a fan is sometimes used for 
cooling. A machine suitable for delivering 150 amp. for weld- 
ing weighs approximately 400 lb. (181 kg.) ; thus it is obvious 
that two men may carry it around to some extent, although if 
it is to be widely portable as is required in most places where 
portability is necessary at all, a truck must be used either for 
this type of welder or for any of the previous types of direct- 
current welders. 

Since there is no less in resistance and since the transforma- 
tion is done by a transformer, it is a fact that the efficiency is 
very high compared with that of any direct-current apparatus. 
However, for protective reasons, it is necessary to have very 
large leakages in the transformer, which results in an over-all 
efficiency considerably less than that of a standard constant- 
voltage transformer. The cost also is low. 

Among operating characteristics of the alternating-current 
welder which are emphasized by the manufacturers is the short 
arc obtained, which gives less chance of burning the weld. How- 
ever, arcs greater than x /2 i n - (1.2 cm.) in length have been 
established by the writer with a covered electrode, although it is 
a fact that with the bare electrode a short arc only can be main- 
tained. Furthermore, the welds obtained were not so perfect as 
the manufacturers claim should be produced regularly with this 
type of apparatus. 

Some of the difficulties, as seen by the users of these machines, 
follow: (1) Heat is equal at both electrodes; (2) alternating- 
current welders cannot be used for carbon electrode work; (3) 
power factor is low; (4) considerable skill is necessary to hold 



ELECTRIC FURNACES, WELDING, ETC. 283 

the arc at all with bare electrode; (5) speed of operation is rela- 
tively low; (6) the weld is liable to be poor when using bare 
electrodes because of the frequent breaking of the arc, and (7) 
the arc tends to sputter considerably, using more electrode than 
if this did not occur. 

In discussing these points it is self-evident that the heat at 
each electrode must be the same. With the direct-current welder 
the heat at the point where the most heat is required can be 
secured by making that electrode positive. This is very essen- 
tial where heavy plate is being welded. 

The alternating-current arc is not suitable for carbon-electrode 
work because when the electrode is positive carbon is carried 
across the work, thus very greatly changing the characteristics 
of the weld. 

A power factor of approximately 10 per cent is usually neces- 
sary to maintain the arc at all, and a power factor of 5 per 
cent gives considerably better operation. This means that for 
an outfit which would normally deliver 3 kw. to the arc trans- 
former connections the power-house capacity and line capacity 
necessary to serve it must be 30 kw. at 10 per cent power fac- 
tor. 

The speed of operation is low because it is more difficult to 
hold the arc ; it is practically impossible under normal operating 
conditions for any man to hold the alternating-current arc con- 
tinuously during a ten-hour day. 

Any arc welder is good or bad, depending upon the amount of 
oxide included in the metal. Each time that the arc is broken 
there is very apt to be a little pocket of oxide formed; conse- 
quently there is very great possibility that each time the alter- 
nating-current arc breaks a defect in the weld will be occa- 
sioned. Because of the difficulty of holding the arc the weld is 
less reliable. 

Cost of Operation. The sputtering of the electrode is some- 
thing that cannot be explained positively. It probably comes 
from very wide variation in heat being liberated at the arc dur- 
ing different parts of the cycle. The fact still remains that the 
arc sputters very considerably more with alternating current 
than with direct current. 

Considering the cost of operation, there are three important 
items: (1) Cost of equipment; (2) cost of equipment supply- 



284 ELECTRICAL AIDS TO GREATER PRODUCTION 

ing the power, and (3) cost of labor in doing the welding. All 
three of these can be determined with fair accuracy. 

The first cost of a 150-amp. alternating-current welder is about 
$150 and that of a direct-current equipment about $1,000. The 
relative cost of generating and line equipment for the alternat- 
ing-current welder is about .$170 per kva., and for the direct- 
current set about $225 per kw., or $5,100 and $680 respectively 
for 3-kw. sets. The comparative labor costs are approximately 
100 per cent for direct current and 125 per cent to 150 per cent 
for alternating current. Where power is purchased the cost of 
energy for the two types should be considered in place of the 
second item above. If the rate is not based on power factor or 
kva. input (compared with kw. input), the cost may be less for 
alternating-current equipment because of its higher efficiency. 
However, based on the making of a certain weld, this advantage 
for alternating-current apparatus would probably be offset. At 
any rate, many central stations are now penalizing for low power 
factor, so the cost of power will most likely be higher for alter- 
nating-current welders. 

Comparative labor costs in one of the large shipbuilding plants 
have been ascertained. The best operator on alternating-current 
apparatus could do about two-thirds as much work as the best 
operator on direct current. With an operator of less skill the 
direct current could be operated in a fairly satisfactory way, but 
the alternating-current outfit could not be operated. 

There are no doubt improvements which will be made over the 
present type of alternating-current welding apparatus both as 
regards operating characteristics and cost which will improve 
both. For instance, one of these is to use, instead of a trans- 
former, a reactance with a variable magnetic circuit. This will 
improve the characteristics and at the same time reduce the cost. 



DATA ON SPOT WELDING 

To decide whether it is better to rivet or to spot-weld an 
article one must take into consideration the use of the article and 
must not base his decision on the cost of obtaining a desired 
strength. In light work spot welding can successfully replace 



ELECTRIC FURNACES, WELDING, ETC. 285 

riveting in 90 per cent of the cases. There are numerous condi- 
tions where it is impossible to use rivets because the stock will 
not permit the punching of the hole or because the rivet head is 
objectionable. Special spot-welding machines can be made to 
take care of the difficult shapes and thus reduce the cost of an 
article in the saving of the rivets and dies, maintenance of dies 
and labor in laying out and punching the stock. 

An ideal condition for spot welding, says G. A. Hughes, elec- 
trical engineer of the Truscon Steel Company, Youngstown, 
Ohio, is where a smooth surface is desired and the material' does 
not permit the countersinking of the rivet heads. But spot 
welding is not confined to the sheet-metal industry alone. Struc- 
tural steel can be successfully welded. In fact, it is being used 
in shipbuilding to advantage. The question that arises is, 
"What is the greatest thickness of material that can be success- 



TABLE XXX— DATA OBTAINED USING THREE %fc-IN. PLATES 















Auto- 


Time 














Tap of 












Size of 


Condition 


Trans- 


in 


Volts 


Amp. 


Kw. 


P.F. 


Spot, In. 


of Materials 


former 


Seconds 


232 


186 


17.6 


0.41 


7 /l6 


Free from rust 


5 


44 


232 


176 


18.4 


0.45 


7 /l6 


Free from rust 


5 


42 


232 


180 


18.1 


0.43 


7 /l6 


Free from rust 


5 


44 


230 


256 


25.6 


0.43 


7 /l6 


Free from rust 


7 


30 


230 


248 


24.0 


0.42 


7 /l6 


Free from rust 


7 


31 



TABLE XXXI— DATA OBTAINED USING TWO % 2 -IN. PLATES 













Tap of 












Time in 


Auto- 
Trans- 


Condition of 


Volts 


Amp. 


Kw. 


P.F. 


Seconds 


former 


Material 


218 


208 


26.4 


0.57 


24 


7 




218 


224 


26.0 


0.53 


22 


7 


-(-3 , 


218 


224 


26.4 


0.53 


24 


7 


3 c 


218 


228 


26.8 


0.54 


22 


7 


^d a> 
c f-> 


218 


216 


26.0 


0.55 


22 


7 


c§ ^ 


218 


224 


26.4 


0.54 


26 


7 


r-5 U 


218 


220 


25.5 


0.53 


25 


7 


CO ^ 


218 


224 


28.0 


0.57 


22 


7 





286 ELECTRICAL AIDS TO GREATER PRODUCTION 



TABLE XXXII— DATA WITH DIFFERENT MATERIAL 

Tap of Size 

Auto- of 

Time, Trans- Spot 

Volts Amp. Kw. P.F. Material Used Seconds former In. 

220 244 24 0.54 Two 9&-in. mild-steel 

plates 15 7 % 

220 260 20 0.35 Two %6-in. Vasco non- 

shrinkable steel 



plates 



20 



3 s 



TABLE XXXIII— COMPARISON i OF SPOT- WELDED AND RIVETED 

JOINTS 





Size of 


Condition of Sheets, 


Maximum 


Nature of Number 


Test No. Spot, In. 


and Contacts 


Load, Lb. 


Failure of 


Spots 


1 


%6 


Free from scale, 
Contacts good 


4,460 


Welds pulled out 


1 


2 


%6 


Free from scale, 
Contacts good 


7,250 


Welds pulled out 


2 


3 


5 /l6 


Free from scale, 
Contacts good 


10,920 


Welds pulled out 


3 


4 


%6 


Scale on sheets, 
Contacts poor 


4,400 


Welds sheared 


2 


5 


%6 


Rust and scale. 
Contacts good 


8,100 


Welds sheared 


3 


6 


Two-^-in. 


rivets, holes drilled 


4,700 


Rivets sheared 






and rivets inserted with care 








7 


Two- % -in. 


rivets, holes drilled 


5,200 


Rivets sheared 






and rivets inserted with care 









fully welded?" The thickness of material will depend entirely 
upon its size and shape, together with the rating of the welding 
machine. The writer has seen two pieces of ^-in. (1.27-cm.) 
material — a total thickness of 1 in. (2.51 cm.) — welded on a 
30-kw. machine. 

The data are intended to give an idea of (1) power consump- 
tion, (2) strength of the weld, and (3) speed at which welds 
can be made. All the tests on which the data are based were 
made on 30-kw., 220-volt, 60-cycle hand-operated machines made 
by the Federal Welding & Machine Company of Warren, Ohio. 
The machines were in service for two hours before the tests were 

i All tests were on No. 14 gage sheets, steel 3 in. wide, single lap-joint, 
single-shear. 



ELECTRIC FURNACES, WELDING, ETC. 287 

made. This was to allow for the heating of the machines. Each 
machine had .an anto-transf ormer in the primary circuit of the 
welding transformer to control the welding circuit. Taps were 
provided on the auto-transformer to adjust the primary voltage 
in eight steps from 65 per cent to full-line voltage. 



TABLE XXXIV— TENSION TESTS ON SPOT-WELDED JOINTS 



Test No. : 


1 


2 


3 


4 


Maximum load, lb. 
Nature of failure 

Number of spots 
Kind of joint. . . . 


3,700 
Weld pulled 

out 
1 

Lap 
Single shear 


3,740 

Weld pulled 

out 

1 

Lap 

Single shear 


6,470 

Weld pulled 

out 

1 

Butt 

Double shear 


6,195 

Weld pulled 

out 

1 

Butt 

Double shear 


Test No. : 


5 


6 


7 


8 


Maximum load, lb. 
Nature of failure 

Number of spots 
Kind of j oint .... 


4,980 
Weld pulled 

out 

2 

Single shear 

Lap 


4,980 

Weld pulled 

out 

2 

Lap 

Single shear 


7,830 

Plate, failed 

2 

Butt 
Double shear 


7,790 

Plate failed 

2 

Butt 
Double shear 



In making the test recorded in Table XXX three plates of soft 
steel % 6 in. (4.8 mm.) thick were used, making a total thickness 
of % 6 in. (13.2 mm.). The first three welds were made with 
the auto-transformer on tap 5. The time of welding varied 
from forty-two to forty-four seconds and the power demanded 
from 17 kw. to 18.4 kw. The fourth and fifth welds were made 
with the auto- transformer on tap 7. The time of welding was 
thirty to thirty-one seconds and the power demanded 24 kw. to 
25.6 kw. All of the welds were satisfactory. (Note the power 
factor.) An attempt was made to weld on tap 8, but this was 
unsuccessful as the material next to the copper contacts would 
become hotter than the center plate and would be forced out 
from under the contacts and thus burn the material at point of 
weld. 

An attempt was made to determine the proper pressure for 
the contacts while welding, since the presence of the scale and 
rust caused considerable arcing and burning of the material 
under the contacts, forcing the molten metal out and thus leav- 



288 ELECTRICAL AIDS TO GREATER PRODUCTION 

ing a bad weld, although it would have the appearance of a 
perfect one. Upon cutting into the weld, however, it would 
have the appearance of a honeycomb. To' avoid this trouble it 
was decided first to burn the rust and scale off. This was ac- 
complished by forcing the welding contacts firmly on the mate- 
rial and then turning the power on the welder for a moment. 
This method removed the scale and assured a good contact be- 
tween the welding points and the material. Then the power 
was turned on and the material brought up to a welding heat 
without arcing. This saved the cleaning of the stock and added 
about 50 per cent to the life of the welding points. 

To determine the kilowatt-hours consumed in a day's run an 
integrating watt-hour meter was installed. Some conclusions 
made from these readings are given: 

Material tested — No. 16 gage sheets, 3 in. wide; wields %-in. spots. 
1480 welds of two pieces No. 18 gage sheet steel. 
1050 welds of four pieces No. 16 gage and one piece %6-in. plate. 



2530 welds total in ten hours. Energy consumed, 42 kw.-hr. 

680 welds of two pieces No. 18 gage sheet steel. 
1350 welds of four pieces No. 16 gage and one piece %6-in. plate. 
545 welds of one piece of No. 18 gage and one piece of %-in. mild steel. 



2575 welds total in ten hours. Energy consumed, 35 kw.-hr. 

The number of welds made in a ten-hour period was not large 
owing to the nature of the material, it requiring three men to 
handle the work and one man to operate the machine. The 
result of tension tests on spot welding are given in Table 
XXXIV. Table XXXIII compares the use of ^-in. rivets and 
spot welding. 



WELDS AS A SUBSTITUTE FOR RIVETS 

Electric welding as a substitute for riveting is being tested 
by the government at four shipbuilding yards, and so far the 
work is proving highly satisfactory, says the Marine Review. 
According to recent data, the process will increase the strength 
of the joint at least 25 per cent and decrease the time to get out 



ELECTRIC FURNACES, WELDING, ETC. 289 

a hull nearly 50 per cent. Eminent marine engineers claim that 
there will be a saving in labor of 60 to 70 per cent. The machine 
employed is the Wilson welder. At present the plates are being 
lap-welded, the plates being overlapped at least 2 in. (5.1 cm.), 
sometimes more, and each edge welded down. In the future it 
is the intention to butt-weld the plates, in which case they will 
be beveled so that when placed edge to edge V-shaped grooves 
will be formed, into which the welding metal will flow, leaving a 
welt over the top of the V. The reverse side, the one exposed 
to the sea, will be left perfectly smooth. By this method con- 
siderable steel will be saved which otherwise is wasted by over- 
lapping, and at the same time the weight of the ship will be 
reduced. Plates 3% in. (8.9 cm.) in thickness have been welded, 
this being the maximum thickness used on the particular jobs 
where observations are being made. The advisability of casting 
entire steel sections and then welding them together is also under 
consideration. While electric welding will eliminate the use of 
rivets to a large extent, there is at present a certain amount of 
riveting to be done in attaching the plates to the frames. It 
is estimated that thirty welders can do the work of 125 riveters. 
The Wilson welding outfit operates on what is known as the arc 
principle and consists of a motor-generator set, the generator 
of which is wound for 35 volts. The welding metal serves as 
one electrode, while the ship plates constitute the other electrode. 



ELECTRIC HEATING VERSUS OTHER METHODS 

P. H. Mitchell compares the relative amounts of heat which 
can be produced for one cent with various fuels and electricity 
at different prices as follows: 

B.t.u. 

Anthracite at $8" per ton 18,000 

Anthracite at $10 per ton 14,300 

Bituminous coal at $3.50 per ton 48,000 

Bituminous coal at $7 per ton 24,000 

Peat at $4 per ton 21,000 

Fuel oil at 7 cents per gal 15,500 

Fuel oil at 14 cents per gal 7,750 

Electricity at 1 cent per kw.-hr 3,413 

Electricity at 0.8 cent per kw.-hr 4,240 



290 ELECTRICAL AIDS TO GREATER PRODUCTION 

From this lie concludes that electric heating is feasible at $12 
per horsepower, but that it is not yet an economic possibility, 
due to high cost and lack of available power. Electric power 
rates would have to be one-quarter of the present rates for elec- 
tric heating to compete with heating by anthracite coal. Many 
millions of horsepower would be required to meet even present 
requirements. 



CHAPTER VI 

METERS AND MEASUREMENTS AS 
APPLIED TO INDUSTRIES 

USES OF THE GRAPHIC METER 

It is always wise before undertaking to motor drive equipment 
to find out what the real conditions are rather than to rely upon 
assumptions. In the early days of motor applications the be- 
setting sin of everyday practice was installation of motors con- 
siderably too large for the job. This fault was generally an un- 
happy inheritance from steam-engine practice, in which it was a 
custom to install an engine as large as would probably be needed 
and then a couple of sizes larger still for good measure. When 
the electric motor came along there was a very strong tendency 
on the one hand to order, and on the other to sell, a machine of 
about the same rated output as the previous engine without fur- 
ther investigation. The penalty paid for this indiscretion was 
high first cost, low efficiency, and in the case of alternating- 
current motors abominably low power factors. Later people 
began to make experimental tests of the power actually required, 
and then reform began. By means of the graphic meter it is 
easy to find out exactly not only the output which may be re- 
quired but also the distribution of that output through the day's 
work, often economically more important than the actual work 
required. In these days, when charges for electrical energy are 
commonly based on demand as well as energy required, the 
nature of that demand is of large economic importance, and this 
is precisely what the graphic meter provides ready to hand. It 
shows not only how much energy is required but hour by hour 
the probable range of variations. Indeed, it goes further and 
gives an exceedingly good line on the general activities of the 
shop, sometimes with results important to the cost of produc- 
tion. 

There are two general varieties of graphic meters, each of 
them important in its own sphere and considerably used. The 

291 



292 ELECTRICAL AIDS TO GREATER PRODUCTION 

familiar dial instruments are extremely convenient for rough 
determinations of demand in terms of time, and from their sim- 
plicity they can be very handily used in keeping records over a 
considerable period. TThile not attempting accurately to regis- 
ter the quick variations which sometimes appear, for many uses 
they are quite sufficient. The curve-drawing instruments work- 
ing on a continuous roll capable of a variety of speeds and giv- 
ing results in rectangular co-ordinates which can readily be 
graphically integrated meet another class of requirements — 
those which require a close measurement of power involving 
quick variations. Cases of this sort arise in connection with 
some machine tools having a cycle of operations in which the 
input is necessarily very variable from time to time. Such 
graphical instruments often give extremely valuable hints for 
improvements in design and management. Their place is to fill 
the gaps necessarily left by the simpler and rougher recorders 
whenever close analysis becomes necessary. Both classes of re- 
corders have their necessary uses, and both should be employed 
much more frequently than they are. even at the present time 
when their value has already become well established. 

As an example of what can be done with graphic meters the 
following case will be cited : 

Speeding Production by Using Graphic Meters. In its plant 
at San Francisco. Cal.. the National Paper Products Company 
has spent considerable money to install circuits and graphic- 
metering equipment to check the operations of its machines and 
men. The machines, which are of the type required to fabri- 
cate paper in rolls into paper products such as paper cans, 
crimped paper novelties and the like, are driven mostly through 
direct connection by fifty-three motors ranging from 0.5 hp. 
to 10 hp. in size. Every motor is arranged for connection to 
the checking circuits. The design of the checking system is such 
that its control is centralized in the office of the general manager 
of the plant. No one except this officer of the company knows 
what combinations of switches will check the different machines, 
but all of the employees are aware that some machine and its 
operator are continually under scrutiny. 

The need for such a system has been well explained by A. L. 
Bobrick. the general manager. He said: "The principal object 
in installing this equipment was to get an absolute record of the 



METERS AND MEASUREMENTS 



293 



running time of our machines and to check up the report sheets 
turned in by the operators every day. In the paper-converting 
business there is a great deal of time lost in making changes on 
the machines, and our big problem is to keep all of our machines 
running to full capacity at all times, as our profits depend upon 
the tonnage we can convert per day. 

"Every morning at 10 o'clock I have production reports on 
my desk, showing just what each machine has done for the last 
twenty-four hours, this report being up to 8 a. m. of that morn- 



ON REGULAR 

SWITCHBOARD 





SWIT&NOYJL 



ON BOARD N0.5. 



A MOTOR STARTER 

AND SWITCH T oTESTIN6BQARh 
ON4™FLOOR 



TESTINGBOARD 
NO. 4 



TO TEST! NQ BOARD 
ON 3"" FLOOR 



TESTING BOARD 
NO. 3 



TO TESTING BOARD 
ON ?»° FLOOR 

TEST) 



FOUR N0.4 CABLES AND ONE NO/4 WIRE 
IN CONDUIT 

3<? €02,220 V. 
MAIN SOURCE 
OF POWER ■> 
ABOUT 100' •- 

Fig. 82 — Some Features of Pyrometer Installations 




NO, 2 



6th 
Floor 



ing. Our meter is always on some machine in the building. I 
usually take reports of about four machines during the twenty- 
four hours, and these reports are compared with the production 
report of the particular machine. If there is any discrepancy, 
either a mistake of the operator or falsification of the report, it 
shows up. 

"Since most of the operations in the paper-converting indus- 
try are cutting and since the machine uses more power during 
the cut, it is very easy to obtain a clear record showing distinctly 
each operation." 



294 ELECTRICAL AIDS TO GREATER PRODUCTION 

The electric features of the system are of especial interest. 
The apparatus consists of an Esterline 220-volt, 5-amp. poly- 
phase graphic wattmeter with switchboard and circuit arrange- 
ments to connect it easily to any motor or group of motors in the 
plant. This meter, together with two 50/5-amp. current trans- 
formers, three 30-amp., single-throw, four-pole, non-fused 
switches, one single-throw, two-pole, non-fused switch and two 
30-amp. fuse clips with two 5-amp. fuses, is mounted on a panel 
in the executive office. On this panel clips are also provided 
under two of the switches for short-circuiting the secondary 
windings of the instrument transformers when they are not in 
use. 

When the plant was originally wired for motor drive, dis- 
tribution panels were installed on each floor with a knife switch 
in each motor circuit. Alongside each of these panels an addi- 
tional panel, also equipped with knife switches of the same size, 
was installed to carry the checking system equipment. 

The checking system circuits are laid out so that by manipu- 
lation of the switches on the office switchboard and on the panel- 
boards on each floor any motor can be taken off its regular sup- 
ply circuit and transferred to a circuit running through the 
metering equipment in the office without interrupting the flow 
of energ}' to the motor. The method by which this is accom- 
plished can be easily understood by reference to the wiring dia- 
gram (Fig. 82), which shows complete connections between the 
source of power and one motor. This diagram also indicates 
where similar taps are made for motors on other floors. To 
keep secret the switching arrangement the knife switches on the 
panels in the factory are numbered and the number combina- 
tions are known only to the general manager. These switches 
are opened and closed only on his orders. The effect of opening 
and closing them is to connect certain motors through the office 
and disconnect the regular supply. 

In actual operation there are two or three methods of using 
this equipment. First, the meter may be switched on a certain 
machine and the chart arranged to feed at the rate of 6 in. (15.2 
cm.) per hour. This method can be used to check a production 
record for the machine. Such a chart as that shown in Fig. 83 
will then be produced. It clearly indicates the machine stops 
made by the operator on the 64-in. (162.6-cm.) corrugator, which 



METERS AND MEASUREMENTS 



295 



in this instance was under observation. If a more detailed study 
of a man's ability to run a machine to its limit is desired, the 
meter can be set to run at 6 in. (15.2 cm.) per minute. This 
produces a record like that in Fig. 84 and shows every individual 



i.o 

0.9 
0.6 
0.7 

0.6 

0.5 

0.4 

0.3 

02 

01 




ooooooooo;ooo'oooo 
£90 1=45 I 30 1:15 1-00 IZ445 





Figs. 83 and 84 — Graphic-meter Chart from Motor Driving Large Cor- 
rugator, and type of record used to study and compare speeds of 
Operators 

In making the first record the chart speed was 6 in. per hour; with the 
second it was 6 in. per minute. The chart in Fig. 84 was obtained on a 
crimping machine for 4%-in. paper cans. The input (in kw.) to the 0.5-hp., 
220-volt, three-phase, 60-cycle motor driving the machine can be obtained 
for any instant by multiplying the ordinate by 2. Every deflection means 
one can crimped. 

operation. In this case the record was taken on a 0.5-hp., 220- 
volt, three-phase, 60-cycle motor driving a crimping machine 
making 4J-in. (14.4-cm.) paper cans. Every peak on the chart 
means one can crimped. The closely grouped and lesser fluctua- 



296 ELECTRICAL AIDS TO GREATER PRODUCTION 

tions show idle time. A third method of operation is to connect 
through the meter the motors of two or more machines of differ- 
ent horsepower ratings and different characteristics. With this 
plan a record will be produced which can be interpreted by one 
with a prior knowledge of the characteristics of the machines. 
Mr. Bobrick has been able to take intelligible records on four 
machines at once by this method This, however, is a possibility 
that developed after the system was installed, as it was orig- 
inally intended to give only the records of one machine at a time. 

A SIMPLE METHOD OF FINDING MOTOR LOAD 

Although motors in a properly equipped factory are supposed 
to operate at or near full rating most of the time, the assump- 
tions on which the motor ratings were based may be in error or 
the load may have changed, so that it is advisable to test the 
power required by motors from time to time. If this is not done, 
the motors may operate at less than rated load unnoticed and 
the power factor (if they are induction motors) and efficiency 
will suffer thereby. While arrangements for connecting in port- 
able ammeters are preferable, the power required can be easily 
checked, points out Willard S. Wilder of the meter and testing- 
department, Milwaukee Electric Railway & Light Company, by 
observing the number of disk revolutions in the watt-hour meter 
connected with the motor circuit. Of course, if other motors 
or apparatus are served from the meter, they must be discon- 
nected while the test is being made. 

For most General Electric, Duncan, Sangamo and Fort Wayne 
meters the watt-hour constant will be found painted on the edge 
of the disk. On the Columbia meters the constant is on the name 
plate, while on the Westinghouse meters the constant cannot be 
found on the outside of the meter. By the use of the accompany- 
ing table the watt-hour constant can be determined for any 
meter, after obtaining from the name plate on the meter the 
make, type and capacity in amperes of the meter. 

Since the watt-hour constant is the number of watt-hours con- 
sumed during one revolution of the meter, all that is necessary 
to do in order to compute the power (watts) demanded is to 
count the number of revolutions of the disk during one minute 
and multiply by sixty times the watt-hour constant. 



METERS AND MEASUREMENTS 297 

As an example, take a Westinghouse type OA meter, 110 volts, 
10 amp. rating. From the table the watt-hour constant is found 
to be 2/3. Then, operating the apparatus that it is desired to 
test, taking care that no other electrical device is drawing energy 

TABLE XXXV— TESTING CONSTANTS FOE 110- VOLT, 60-CYCLE 
STANDARD WATT-HOUR METERS i 

Make of Meter Type of Meter Capacity in Amperes 

3 5 10 15 20 25 40 50 
General Electric.. J; J-l; JN; FN; 

D-l; DN % 0.5 0.5 1.0 .. 1.0 .. 2 

General Electric 2. 1; 1-8; 1-14 % 0.3 0.6 1.0 .. 1.5 .. 3 

General Electric 3. C; C-5; C-6; C-9; 

J-2; D-2 V 8 0.2 0.4 0.6 .. 1.0 .. 2 

Westinghouse 3 . . . A ; round Ve V3 . . % . . % 

Westinghouse 3 . . .B; C; OA; D; C . . % % 1 % % % m 

Fort Wayne * K; K x K 2 K 3 (above 

serial No. 345,000) 0.25 0.5 0.75 1 1.25 2 2.5 

Sangamo F 1/2 % . . % . . % 

Sangamo D % % . . % . . % 

Columbia 3 ..... .All %s % % . . 25 /is . . 2% 

Duncan No. 150,000) . . . 0.25 0.5 1 . . 1 . . 2 

1 For 220-volt meters double the constant. 

2 For polyphase meters double the constant. 

3 For three-wire and polyphase meters double the constant. 

* For three-wire meters double the constant ; for polyphase meters multi- 
ply the constant by four, except type K 3 polyphase meters, for which the 
constant is doubled. 

at the same time, the number of revolutions of the meter disk 
for one minute on are counted. Suppose this came out thirty 
revolutions. Then the power demanded would be 30 X 60 X 
2/3 = 1200 watts. 

A table could be prepared in which sixty times the watt-hour 
constant would be given, but this might not be convenient to use 
when it was desired to count the revolutions for less or more than 
one minute. If the timing period is other than one minute, the 
multiplying factor is watt-hour constant -=- period in hours. 



METHOD OF TESTING METERS AT TWO POWER 

FACTORS 

A meter-testing panel has been developed by Joseph N. 
M'Clurg, foreman of the meter department of the Scranton 



298 ELECTKICAL AIDS TO GREATER PRODUCTION 

Electric Company, which may be helpful in testing single or 
polyphase meters of 0.5-amp. to 100-amp. ratings at 110, 220 
and 440 volts. It is represented in Fig. 85. 

I/O Volts Single Phase 



^<3 



FUSE* 



A 2 • 



4& 



A, : • I 

SELECTOR 
SWITCH 



AAAAA 



'Ground Wire 



I.I.I.IIIII 






440 Volts, 



5^_ 



WW vwv vwv 

LAPI 




A, 




RHEOSTAT 
METE I? 

QrlfTEl? LEADS'^ 

CALIBRATOR" 
POTENTIAL 

'■P OTENTIAL TERMINALS G 9 9* 




1 10 Volts 



440-3? 
j Supply 

Power 

Voltage Factor Conn 
110 50 0-A, 

100 

220 50 

100 

440 50 

100 



0-A, 
0-3? 
OS, 
OC z 

o-c, 



Y220Volts* -'A ■ Phase Relation 

B, B? A? between Transformer 

zKw.*t40/220-JI0 Transformers Taps 



Fig. 85 — Wieing Diagram and Phase Relation Between Transformer 

Taps 



The load consists of old direct-current arc-lamp resistance coils 
connected with an old 5-kw., 2200/110-volt transformer operated 
at reduced voltage to obtain 20 volts on the secondary. The 
selector switch gives 110-220-440 volts, 50 and 100 per cent 
power factor. The connections for giving different voltages and 
power factors are indicated in the accompanying diagram. 
Switch E is closed when testing single-phase meters, one poten- 
tial lead being fastened to the line terminal of the series coil in 
the meter. This switch is opened if the potential coil is not 
joined with the current coil. It has individual terminals. 

From the vector diagrams at the bottom of the illustration it 
may be seen that if the load current is in phase with vector OC lt 
OA x or OB x , 100 per cent power factor will be obtained by con- 
necting selector switch with contact A ± , B ± or C ly the voltages 
being 110, 220 and 440 volts respectively. AVhen connected with 



METERS AND MEASUREMENTS 299 

A 2 , B 2 or C 2 , however, the voltage is 60 deg. out of phase with 
the current, so 50 per cent power factor will be obtained. 

TESTING THE LOADS ON DISTRIBUTION 
TRANSFORMERS 

A transformer testing outfit that consists of a split-type cur- 
rent transformer with two windings connected to a low reading 
ammeter with a 48-ft. (14.6-ni.) duplex stage cord is used by 
the Portland Railway, Light & Power Company of Portland, 
Ore. Two scales, one for each winding, were calibrated with 
standard Instruments. The low scale has a range of from 5 amp. 
to 40 amp. and the high scale from 45 amp. to 150 amp. A 
two-point dial switch mounted on the side of the current trans- 
former is used for changing scales. The contact bar on this 
switch touches one button before leaving the other, so that in 
changing from one scale to the other the circuit is not opened. 

All testing is done on the secondary side of the transformers, 
generally in the outside legs only, and in each direction from 
the transformer. In this way the total load on the transformer 
is obtained. The conditions of balance between the two sides of 
the line are shown and also how near the transformer is to its 
center of load. 

In using this outfit it is, of course, necessary to test at a time 
when the peak load is on. 

In addition to testing transformers, this outfit is frequently 
used to test motors and also to test the current in 2400-volt cir- 
cuits to determine how the current in the three phases was bal- 
anced up and to determine the load on a branch circuit. This 
scheme was suggested by W. C. Heston and R. E. Thatcher. 



CHAPTER VII 

HANDLING MATERIAL IN INDUSTRIAL 
PLANTS WITH ELECTRIC TRACTORS 

For handling materials in industrial plants the electric indus- 
trial tractor has unique advantages. It is handled with extreme 
ease even by comparatively inexperienced men. It is economical 
in service, quick in operation and entirely free from the fire 
dangers which tend to discourage the use of gasoline trucks in 
and about buildings. The truck for this purpose is developed 
in the form of a tractor which picks up loaded trailers and 
transfers them from cars to storage or vice versa, thereby dis- 
pensing with a very large amount of manual labor and a corre- 
sponding amount of expense. It should be noted in this con- 
nection that electric power is one of the few things which has 
not advanced materially in price, while war conditions have 
greatly enhanced the wages of even the most inexperienced 
workers. Most of the work around industrial plants has cus- 
tomarily been done by hand trucks, slowly and at large expense. 
The tractors, handling loads up to about 25 tons, do the large 
amount of actual haulage necessary with far greater rapidity 
and at a much lower cost, requiring a reduced number of men for 
the actual work of transferring the goods from the tractor back 
to the cars in half an hour the tractor can do the same haulage 
that would require six men for three hours, while itself requir- 
ing the services of only two men, leaving the rest of the gang 
free to speed up the actual work of loading. 

The following information by F. C. Meyers, formerly with the 
Society for Electrical Development, relates to some specific cases : 

Table XXXVI shows some statistics on electric industrial-truck 

freight moving taken from one of the most representative steam 

railroads operating east of the Missippi. There are shown the 

saving in time and the reduced amount of labor required — both 

of which spell money, the money that railroads need and are 

begging for. Other data show some typical instances of economy 

in labor and time in freight handling o£ various commodities^ 

300 



ELECTRIC TRACTORS 301 

TABLE XXVI— PERFORMANCE OF TRACTORS 

DAY OPERATION ( TWO TRACTORS ) , ELEVEN GANGS, FORTY TRUCKERS 

Total amount of tonnage handled, lb 1,624,733 

Average tonnage per gang, lb 147,703 

Average truckers per gang 3.6 

Average number of pounds per trucker 41,029 

NIGHT OPERATION (FOUR TRACTORS), FIVE GANGS, THIRTEEN TRUCKERS 

Total amount of tonnage handled, lb 643,058 

Average tonnage per gang, lb 128,611 

Average truckers per gang 2.6 

Average number of pounds per trucker 49,466 



The figures show that in the day operation with eleven gangs, 
assisted by two tractors indiscriminately helping, the average 
tonnage per trucker was. 41,029 lb. (about 18,600 kg.), or 20.5 
tons per day. In the night operation, which Avas made a full 
tractor operation with four tractors doing all the work for five 
gangs and a man less per gang than in the daylight, the average 
tonnage per trucker was 49,466 (about 22,400 kg.), or 24.7 tons 
per night. From these figures it will be observed that for this 
day's work full tractor operation shows an increased tonnage 
per man of 4.2 tons over that of mixed hand and tractor opera- 
tion. 

The tractor in one-half hour does the work of six laborers in 
three hours, or in the ratio of thirty-six to one. In minor opera- 
tions, such as towing large machinery on a six-wheel truck, drag- 
ging heavy cable chains into and from cars, pulling in shore 
gangplanks and moving large crates of 5000 lb. to 10,000 lb. 
(2267 km. to 4535 km.) each, the tractor did the work of twelve 
men. Two men were required for rollers. 

The labor saving is shown by the comparative figures on labor 
requirements to move miscellaneous freight given in Table 
XXXVII. 

In one instance with hand trucks on a short haul a load of 
49,881 lb. (about 22,600 kg.) required twenty-four men two 
hours. With a truck and trailer 73,097 lb. (about 33,110 kg.) 
required but ten men two and one-quarter hours. On a 200-ft. 
(60.9-m.) longer haul 106,700 lb. (about 48,200 kg.) used the 



302 ELECTRICAL AIDS TO GREATER PRODUCTION 

services of twenty-four men ninety-three hours With hand trucks, 
while with a truck and trailer 173,353 lb. (about 78,500 kg.) 
took only ten men sixty-two hours. With one tractor 48,876 lb. 
(about 22,150 kg.) can be hauled 600 ft. (182.8 m.) in twenty- 
five minutes, but a hand truck requires one and one-half to two 
hours. 

In the case of freight packed up on various piers on trailers 
waiting for tractor, the tractor does in one-half hour what other- 
wise required two laborers three hours each. Only two men, a 
chauffeur and a conductor, are required with electric transpor- 
tation. 

At one place of 10,000 population this railroad is using one 
tractor with two men to move barrels weighing 260 lb. (118 kg.) 
each 450 ft. (137.1 m.) from a "barge to cars up the ramps. The 
tractor moves thirty barrels in three minutes, where formerly one 
man with assistance up the ramps moved one barrel in six min- 
utes on a hand truck. 

At another point the road formerly employed 132 truckers. 
Now it is doing this work with tractors and trailers with seventy- 
three men and is handling 500 tons a month more freight than 
formerly. 

On July 16 at one transfer point there were employed 165 
men; on July 17 tractors and trailers were installed and the 
number of men was reduced to 117, while the freight was han- 
dled more expeditiously than formerly. Since this date the ton- 
nage has increased approximately 500 tons, and the number of 
men has not been increased. 

The following data were taken from installations which have 
proved the industrial truck to be both a time-saving and labor- 
saving device : 

In the handling of lumber 12 in. b}^ 12 in. and 14 ft. to 20 
ft. long (0.3 m. by 0.3 m. by 4.2 m. to 6 m.) fifty pieces were 
carried on each load, a total round-trip distance of 600 ft. (182.8 
m.) with two trucks. Two round trips were made and required 
four men and took thirty minutes' time. This amounted to a 
total of 2000 ft. (609 m.) of board lumber, weighing about 3500 
lb. to 4000 lb. (1578 kg. to 1814 kg.) per 1000 ft. Four men's 
time at thirty minutes, at the rate of 30 cents an hour, would be 
60 cents. The charge for running this machine a full working 
day of ten hours is $1.25, or 6 cents for half an hour. This, 



ELECTRIC TRACTORS 303 

added to labor cost, would be a cost of 66 cents to move 2000 
board feet a total distance of 600 ft. 

In another operation where lumber was handled, the size of 
which was 12 in. by 16 in. by 11 ft. (0.3 m. by 0.4 m. by 3.3 m.) 
long and the total weight 600 lb. (272.1 kg.), six pieces were 
carried on each load, making a total weight of 3600 lb. (1632 
kg.). In one hour, two trucks and eight men moved ninety-six 
pieces of lumber, a total weight of 29 tons, a round-trip distance 
of 800 ft, (213.8 m.). The recapitulations of this show that 29 
tons of lumber, or 16,900 board feet (5151 m.), were moved a 
distance of 12,800 ft. (3901 m.) by eight men and two industrial 
trucks in one hour. The labor, at the rate of 30 cents, amounted 
to $2.40. Wear and tear, depreciation and charge for running 
truck, at the rate of $1.25 for a ten-hour day, would amount to 
25 cents for two hours, which, added to the above cost, would 
amount to $2.65. This is at the rate of 9 cents per ton. 

TABLE XXXVII— COMPARATIVE LABOR SAVING, TRAILERS 
OVER HAND TRUCKS 

Hand Trucks, 
Lb. Trailers Men 

40 boxes oranges 3200 

102 half chests tea . . 7680 

12 casks tobacco 2520 

63 chests tea 4390 

85 pig tins 8075 

146 barrels groceries 3400 

66 boxes oranges 5280 

In the handling of miscellaneous freight three electric trucks 
and ten men moved 53 tons a round-trip distance of 450 ft. 
(137.1 m.) and required five and one-half hours' time. This, at 
the rate of 30 cents an hour, amounts to $16.50, and, added to 
charges against the truck of 28 cents, amounts to $16.78, or at 
the rate of 32 cents a ton. 

In the same operation the following was the cost of handling 
miscellaneous freight by hand trucks. Thirty-three tons were 
carried by six men with hand trucks, four men being required 
to load and unload, a total distance of 375 ft. (111.3 m.) in five 
and one-half hours' time, and this, at the rate of 30 cents an 
hour, amounted to $16.50 to move thirty-three tons, or a total 
of 50 cents per ton, showing a saving of 16 cents a ton in the 



3 


10 


5 


25 


3 


12 


4 


17 


2 


21 


4 


29 


3 


17 



304 ELECTRICAL AIDS TO GREATER PRODUCTION 

use of electric trucks, which covered one and a fifth times the 
distance of the hand trucks. 

In the handling of coffee in bags, the weight of each bag being 
240 lb. (108.8 kg.), a total of 118 tons was carried on tw<? 
electric tracks, which made ninety-eight trips, each 200 ft. (60.9 
m.) long, and required the service of fourteen men for five 
hours. This, at the rate of 30 cents per hour, amounted to $21, 
or allowing $1.20 for wear and tear and depreciation of trucks, 
to $22.20 to move 118 tons, or at the rate of 18 cents a ton. 

TABLE XXXVIII— COMPARISON OF LABOR REQUIREMENTS, TIME 

OF OPERATION AND LOAD WITH HAND TRUCKS AND 

WITH TRACTORS AND FOUR-WHEEL TRUCKS 



Hand Trucks, Tractors 

Aug. 14. 1917 Aug. 21, 1917 



Trucks in line 4 p. m 30 19 

Trucks in line 4.30 p. m 22 22 

All backed up 6.19 p. m. 5.15 p. m. 

All unloaded 6.30 p. m. 5.40 p. m. 

Total number of packages handled 3875 5350 

Coffee in 135-lb. (61.2-kg.) bags for distances up to 160- ft. 
I 48.7 m.) is being handled in one place by electric trucks for 6 
cents a ton. Rags in 500-lb. (226.7-kg.) bales cost up to 18 
cents a ton with hand tracking. Sixty-four 800-lb. (362.8-kg.) 
barrels of plumbago were moved 60 ft. (18.2 m.) in twenty-five 
minutes for 5.3 cents per ton with electric trucks, while sixty- 
three 800-lb. barrels of plumbago were moved the same distance 
in two hours, costing 11 cents a ton, by hand trucking. Four 
men were required to guide and push the hand trucks up an 
incline. 

One hundred and fifty 300-lb. (136-kg.) boxes of rubber were 
moved 75 ft. (22.8 m.) in fifty minutes for 8*4 cents per ton. 
By hand trucks the cost was 18 cents per ton at an Eastern 
terminal. 



CHAPTER VIII 

OUTDOOR SUBSTATIONS 

THE MODERN OUTDOOR SUBSTATION 

When the outdoor substation first appeared as a new and dis- 
tinct type of construction a great many objections were raised 
against it by engineers and operators. Some thought that out- 
door apparatus would not work satisfactorily under conditions 
of cold weather and snow ; others held that it was not advisable 
to expose apparatus to the sun, and again others objected for 
the reason that apparatus placed outdoors would not receive so 
much attention from operators as it does when housed. All 
these and other objections have now been practically overcome, 
says M. M. Samuels, and many of the objectors have been so 
convinced of the advantages of placing high-tension apparatus 
outdoors that they would now strongly object to housing it. 
Thus the outdoor station, although of very recent creation, has 
come to be generally accepted as a matter of course. Most high- 
tension apparatus, regardless of whether it is for indoor or out- 
door service, is now being built to stand up under outdoor con- 
ditions. Outdoor transformers, outdoor oil circuit breakers, 
outdoor metering apparatus and outdoor lightning arresters are 
now standard with all manufacturers of high-tension equipment 
and are as reliable in operation as any indoor apparatus was, 
and perhaps even more so. 

Transformers. — Many improvements in outdoor transformers 
have been made within the last year or two. Terminal troubles 
have practically been eliminated, all high-tension transformers 
now having their terminals on top of the case instead of on the 
side. Furthermore, no more difficulty is being experienced in 
laying out the proper connections to their terminals. The neces- 
sity of climbing ladders or mounting platforms for the purpose 
of reading transformer temperatures and the danger connected 
therewith have been done away with, since modern transformers 

305 



306 ELECTRICAL AIDS TO GREATER PRODUCTION 

are equipped with electrical temperature indicators, which can 
be mounted so that the reading can be done from the ground, 
or where a switchboard is available in a nearby building the 
temperature indicator can be placed on this switchboard. Some 
difficulty is still being experienced when it is necessary to read 
the oil gage, since no indirect method for this reading has yet 
been developed and the gage must be mounted at a considerable 
height near the top of the transformer tank. 

Large transformers of the older type were water-cooled, re- 
quiring elaborate piping and pumping installations, cooling ponds 
or cooling towers. This was always a source of worry to oper- 
ators as well as to station designers, since outdoor piping and 
water pumping were very difficult to design properly, and since 
in the winter time great difficulty was usually experienced in 
maintaining the equipment in good operating condition. Modern 
transformers are therefore being designed for self-cooling. Most 
of the units are of the radiator type, this construction having 
given satisfaction even for large transformers of very high volt- 
age. 

The Oil Circuit Breaker. — Oil circuit breakers of high ruptur- 
ing capacity and designed for voltages of 150,000 have withstood 
the severe operating conditions obtained out of doors and may 
be considered thoroughly reliable. However, with ever-increas- 
ing voltages the oil circuit breaker is increasing enormously in 
size, and it will probably reach its limit soon, when it will be- 
come necessary to develop entirely new methods of switching and 
of breaking the circuit. It is likely that when line voltages go 
up to 250,000 and higher the present type of oil circuit breaker 
will have to be of such large proportions and will require such 
enormous quantities of oil that its use will be impossible. 

Lightning Arresters. — The lightning arrester has also been 
greatly improved within recent months. Many new devices have 
been introduced to prevent the burning out of charging resist- 
ances and the blowing up of tanks. The oxide-film arrester 
which was placed on the market recently promises to overcome 
many of the objections to the older types of arresters, but it has 
not been in operation long enough to make it possible to give 
accurate figures as to its operation, particularly for very high 
voltages and outdoor use. 

Choke Coils. — The improvements made recently on choke coils 



OUTDOOR SUBSTATIONS 307 

are practically all of a mechanical rather than electrical nature. 
Good choke coils have been developed which maintain their shape 
under operating conditions, and the flimsy coils of the past, in 
which the windings often came in contact with each other and 
even melted together, are gradually disappearing. However, 
there does not seem to be any agreement among manufacturers 
as yet on the proper dimensioning of choke coils, such as diam- 
eters, shapes of conductors, number of turns and amount of 
reactance. Since engineers asking bids on choke coils, as a rule, 
do not specify their requirements except as to current and volt- 
age rating, competition tends to make manufacturers reduce the 
copper to a minimum, which, of course, does not result in reli- 
able coils. This subject should be thoroughly considered by 
the standardization committees of the A. I. E. E., the N. E. 
L. A. and other societies interested, and an understanding- 
should be reached as to what constitutes a standard choke coil 
for a given voltage, a given current and a given frequency. At 
present no distinction is being made between choke coils of vari- 
ous frequencies. 

Air-Break Switches. — A great many types of air-break 
switches, disconnecting switches, busbar supports, etc., have been 
developed for outdoor use and have been tried out and found 
satisfactory under all kinds of weather conditions, even though 
this line of apparatus still offers and will continue to offer for 
some time to come a large field for new inventions and develop- 
ments. 

There are two distinct types of air-break switches and me- 
chanically operated disconnecting switches on the market at 
present. In the first type the motion of the blade is affected by 
an insulator which pivots around its own axis. The insulator 
being exposed to torsion at every operation, its top, to which 
the blade is attached, or its pin very often breaks and causes con- 
siderable operating trouble. In the other type the motion of the 
blade is affected by an insulator which rocks around a shaft at 
right angles to the center line of the pin. With this type the 
porcelain is always exposed to a bending moment and breaks 
even more often than with the pivot type. Neither of these 
types, although both give excellent results in many cases, can be 
considered as final. New apparatus will have to be developed 
based upon sounder mechanical principles and operating experi- 



308 ELECTRICAL AIDS TO GREATER PRODUCTION 

ence. Ice and sleet trouble on air-break switches, although partly 
overcome, should still be the subject of thorough study by switch 
designers and inventors if a perfect air-break switch is to be 
developed. The hoods which are generally used as sleet pro- 
tectors do not always serve their purpose ; they very often act 
as accumulators of ice and snow rather than shields. New 
methods will have to be devised to protect the switch contacts. 

Bus Supports. — Various types of bus supports are now ob- 
tainable, suitable for outdoor substations and arranged to ac- 
commodate copper pipe of various sizes, both for horizontal con- 
ductors and for vertical conductors. While the post-type or 
pillar-type supports are both too heavy and too expensive for 
the purpose, petticoat insulators with suitable cap and pin design 
are satisfactoiy for solid (non-flexible) buses in outdoor stations. 
For vertical conductors it is advisable to mount the insulator at 
45 deg. to the horizontal to prevent rain water from accumulat- 
ing on the inside of the petticoats. This can be accomplished by 
the use of properly designed angular pins and angular caps. 
The part of the support which is to be attached to the steelwork, 
be it the pin or the cap, should not have more than two bolt 
holes, so that it can be accommodated on a single steel member. 
If three or four more mounting bolts are used, it is necessary to 
provide two steel members for each support. Either the cap or 
the pin or both should be adjustable so that the support can be 
mounted either on a steel member which runs parallel to the 
conductor or at right angles to same. It is very essential to have 
this adjustment since it is generally necessary to order bus sup- 
port before the station steel design is finished and is not possible 
to tell in advance exactly how each member will be arranged. 

Status of Station Design. In spite of the wonderful improve- 
ments made within the last year or two on outdoor apparatus, 
most of the designs of the outdoor stations themselves are still 
open to a great deal of criticism. Most designers of outdoor 
stations still persist in using the old primitive method of setting 
four heavy steel towers, one in each corner of the station, and of 
connecting these towers in both directions by heavy steel trusses 
and span wires. Many times when it is necessary to make a con- 
nection between pieces of apparatus a span extending from one 
support to another is installed even when the apparatus to be 
joined is close together. This, of course, requires very heav} T 



OUTDOOR SUBSTATIONS 309 

steel work and an endless amount of floor space. In addition to 
this, strain disconnecting switches or other types of hook-oper- 
ated disconnecting- switches are installed at great heights, and it 
is necessary to build high platforms to make it possible to operate 
these switches even when using the clumsy switch hook of 12-ft. 
or 15-ft. (3.7-m. to 4.6-m.) length. Under present conditions, 
when every economy is of extreme value and when the waste of 
steel must be considered a crime, more consideration should be 
given this subject by designers of outdoor substations. 

It is obvious that when strain insulators are used and a strain 
span is installed for every bus, connection or tap the steel work 
will have to be very heavy (strong enough to take care of all the 
pulls to which it is subjected), whereas if a solid bus is used the 
steel work may be comparatively light, since it has only to carry 
the weight of buses, connections and insulators. The tendency 
in outdoor substation design must therefore be to eliminate strain 
spans and substitute solid bus work. 

It must, of course, be admitted that, whereas it is a compara- 
tively easy matter to design a station of the strain-span type, the 
design of a solid bus station requires a great deal of skill and 
designing ability. But when the results are considered it is well 
worth while to apply the best designing skill to developing out- 
door stations which will occupy the minimum of space and will 
require the minimum of steel. 

In addition to the economy in steel, the solid-bus type of sta- 
tion has a great many more advantages as regards safety and 
continuity of operation. For instance, in the strain-span station 
any injury to even one disk insulator may cause a wire to drop 
across the buses, short-circuiting them and thus putting the 
whole station out of service. This is not likely to happen to a 
solid bus. 

In order to reduce the number of insulators in the solid bus 
station to a minimum, tubing should be used for conductors in 
preference to wire or bar. Insulators spaced about 10 ft. (3m.) 
apart on ^-in. (13-mm.) pipe bus will generally give a good 
appearance, whereas when a wire or a bar is used as a con- 
ductor supports will generally have to be installed every 4 ft. or 
5 ft. (1.2 m. or 1.5 m.). 

- In addition to the above-named advantages of the solid bus 
station the possibility of extension must be considered. A 



310 ELECTRICAL AIDS TO GREATER PRODUCTION 

strain-type station is generally dead-ended, and a great deal of 
difficulty is experienced when it becomes necessary to add feeders 
or transformer circuits, whereas the solid-bus station, can be de- 
signed as a unit type, so that any number of circuits can be 
added at any time and it is not necessary to make the initial 
installation of steel work and concrete heavy enough to take care 
of future requirements. 

The general requirements to be met in the design of outdoor 
substations are: (1) simplicity. (2) safety, (3) a minimum of 
steel, (4) a minimum of space, (5) flexibility and interchange- 
ability of circuits, and (6) possibility of extension without dis- 
turbing old circuits. All connections should be made by clamp 
fittings, so that apparatus can be disconnected, removed or re- 
placed without keeping the circuit or the bus out of service for 
an excessive period of time. Soldered or welded joints should 
therefore be avoided as much as possible. When running a pipe 
connection from a transformer or a switch to a bus care should 
be taken to allow for expansion and contraction, otherwise the 
bus may be pulled off its supports or the insulators broken. 
One right-angle turn in each connection will generally be suffi- 
cient for the purpose, and it is never necessary to provide un- 
sightly loops. 

The 45,000-volt station shown in Fig. 86 is a good illustration 
of the unit-type idea. This station shows that with skillful 
designing the unit idea can be applied even when strain insulators 
are used. Strain insulators had to be used in this case because 
they were readily available, whereas solid bus supports could 
not be obtained within the time allowed. It will be noted that 
with this type of design the lines can run into the station from 
any direction. 

The lightning-arrester horn gaps are placed at the very top of 
the structure, and the lines go directly to the gaps and thence to 
the electrolytic tanks without any loops or semi-loops in the dis- 
charge circuit. This arrangement should be adhered to wher- 
ever possible, since a direct path from the line to the arrester is 
always the best. 

Provision is made on the low-tension side of the transformers 
for phasing out. Three bars are installed the full length of the 
three transformers which make up a bank, and connection bars 
are provided from each transformer to these buses, so that when- 



OUTDOOR SUBSTATIONS 



311 



ever it is necessary to interchange a phase it can be done by 
simply interchanging* the connection bars, which are attached to 
the buses by means of clamps. This arrangement is preferable 

J22,000-Volt Lightning-Arrester Horn Oapf 



Outgoing Line /r r rr 




O/iSmtch 

xo-ze ' 



Current Transformer 
.2300 Volt Bus IXjBarr 



Choke 
Coil 



3-1250 Kva. 
Transformers 
?300/22P00-Volt 
60~ 




PLAN B-B 





Lightning 
Arres/er 



Space'fbrlvtuh> 
Circuits 



Cd — : "-|— A ?2jP0Q-Vo/tBuses \ 

r X"=sbbc;""'t 



S^^^^ 7 ^ 




SECTION F-F 

Fig. 86 — 45,000-volt Unit-type Substation 



to the phasing out of the high-tension side of the transformers. 
The low-tension circuits connect with underground cables 
through a set of potheads mounted on one of the steel columns. 



312 ELECTRICAL AIDS TO GREATER PRODUCTION 



Bar connections are provided between the potheads and the low- 
tension transformer delta buses. 

Fig. 87 shows a 45,000-volt station which is similar in type 

Automatic Air Break Switch 




\ 



J fJ*^f-£*A= : 



m 



Operating 
Mechanism 



Wt 









"'''■'■•""'J///V/. 



Bars 



^rnrnr 




: '< i i i : &&K 

■ ' i i 

■ i ii ; • 

[J Lj - 

Cross Section through 
Transformer Wiring 

^Horn Gaps for Lightning Arresters 

J 



.-No. 4 A. WO. 



Lightning 
'Arresters 




'vfy//////', >"-r v/////m//////////;//////)///;//////////mm 



■47-3' 



■—>*<—'- 



Cross Section through 
Line Wiring 

Fig. 87 — 45,000-volt Substation Employing Pin Insulators, thus 
Permitting Use of Concrete Poles 

to the one above, with the exception that it is a solid-bus station 
The use of a solid bus made it possible to use concrete poles 
instead of steel, thus not only reducing the cost but making it 
possible to complete the work in a much shorter time than would 



OUTDOOR SUBSTATIONS 



313 



be possible with steel poles on account of the long delivery on 
steel. If strain buses were used, concrete poles would, of course, 
be out of the question. There are other interesting features in 
this station. It is a combination indoor and outdoor station. 
The 2300-volt switching and the instrument switchboard are 
housed, whereas the transformers and the high-tension switches 
are outdoors. The line is equipped with an automatic air-break 



Air Break Switches 



Main Line 



Air Break Switches 
Mainline 




r>E 
J* ~\-49'-0* 

K9'">l 



SB' 

Section E-E 



Lightning 
Arrester "h 



Disconnecting 
'Switches.. 



'\ Brancfi 
pisconnetfting Lme 

hTransf. 




, «rresn?r w Switches../ 




Section C-C Section D-D 

Fig. 88 — Outdoor Station Equipped With Oil Circuit Breakers and 
Metering Equipment (See Fig. 89) 

switch which was considered sufficient for the present load. 
However, as may be seen in the cross-section, provision has 
been made for the installation of oil circuit breakers to replace 
the automatic air-break switches as the load on the line in- 
creases. 

Two sizes of concrete poles are used in this structure. The 
larger ones, used to support the line equipment, are 33 ft. (10 m.) 



^ 



314 ELECTRICAL AIDS TO 'GREATER PRODUCTION 

long and have 18-in. (45-cm.) square butts and 8-in. (20-cm.) 
square tops. The smaller poles used for the transformer wiring 
are 23 ft. (7m.) long and have 15-in. (38-cm.) butts and 8-in. 
(20-cm.) tops. 

The 33-ft. poles have f-in. 1 19-mm.) reinforcing bars in each 
corner extending the entire length of the pole. Besides these 
there are two rods symmetrically placed in each of two oppo- 
site faces. These additional rods extend from the base 17 ft. 
(5 m.) up the pole. The rods are tied together about every 2 
ft. (60 cm.). To permit attaching the steel cross members used 
in the station lj-in. (32-mm.) standard steel pipe is cast in the 
poles through which to run the clamping bolts. The 23-ft. poles 
are similarly reinforced in the corners but lack the additional 
reinforcing. 



Lightning 
Arrester 




i t 

2300 Volts 



Fig; SO — Schematic Diagram of Connections, for Stations Snowx 

in Fig. 88 

The argument is often heard that whereas in stations of com- 
paratively low voltages a solfd bus may be satisfactory, this con- 
struction is not advisable with stations which must operate at 
very high voltage, because a greater distance must be maintained 
between conductors and because of the extensive use of pole-top 
switches. This is not at all true, since solid-bus stations have 
been designed, built and maintained for 75.000 volts and even 
higher. 

A station in which pole-top air-break switches, vertically 
mounted disconnected switches, oil circuit breakers and outdoor 
metering equipment are used is shown in Fig. 88. High- 
tension metering equipments are now standard apparatus and 



OUTDOOR SUBSTATIONS 



315 



operate satisfactorily. They generally consist of an oil tank 
in which are contained two current transformers and two poten- 
tial transformers, requiring a total of only three high-tension 
terminals, whereas if each current and potential transformer had 
its individual tank a total of six high-tension terminals would be 
required. The meter itself is generally placed in a steel com- 
partment on the side of the metering equipment. If a building 
is nearby, the meters may be installed inside by simply running 
the secondary instrument leads from the instrument transform- 
ers to the metering equipment in an underground conduit or 
overhead on a messenger suspension. 




Wfflvp 



'■la 



3ffPoli 




" Snitch r 
Handle'^ 



'"''r^m^pW^ m)^J? s l^Tr^r- ^W*^. 




k r -'J 



Figs. 90 and 91 — Two-pole Transformer Station and Two-pole 
Sectionalizing Station 



Outdoor substations should be well lighted for the purpose of 
inspection and repair by night. Floodlighting, has been found 
to be not only preferable to other forms of illumination but the 
only satisfactory method, and it is now in common use. 

All of the stations described above which may be considered 
models of modern outdoor stations were designed and installed 
by the J. G. White Engineering Corporation of New York. 



COST OF OUTDOOR SUBSTATIONS 

Data on the cost of outdoor substations are given here that 
apply to the types of construction shown in Figs. 90-92. The 




Fig. 92 — Elevation and Plan of Four-pole Substation 



316 



OUTDOOR SUBSTATIONS 317 

information was obtained from the Southern Illinois Light & 
Power Company of Hillsboro, 111. 

The cost of a two-pole station of this type without trans- 
formers and without the switch structure, which is built sepa- 
rately as shown in Fig. 90, is $773. An itemized statement of 
this expense is given in Table XXXIX below. 

TABLE XXXIX— ITEMIZED COST OF TWO-POLE SUBSTATIOX 

Material $424 

Labor 100 

Superintendence ' 10 

Interest and miscellaneous contingencies 40 

Freight and drayage 100 

Ten per cent overhead 63 

Five per cent engineering and purchasing charges 36 

Total $773 

TABLE XL— ITEMIZED COST OF FO UR-POLE SUBSTATION 

Material $1,219 

Labor 110 

Superintendence 75 

Interest and miscellaneous contingencies . . 50 

Freight and drayage 100 

Ten per cent overhead 156 

Five per cent engineering and purchasing charges 78 

Total $1,788 

The four-pole type of station is used where the load and the 
character of the service required demand the use of electrolytic 
lightning arresters. The company has built this type of station 
in sizes ranging from 150 kw. to 500 kw., but there is no reason 
why the same design could not be employed for even larger sta- 
tions. The installations which have been made to date serve 
towns, but stations of the same design could be used to serve 
such isolated industrial loads as coal mines if housing space were 
not available. The drawing and the bill of material give an 
adequate description of the station. It niay be pointed out that 
the company at first used four-pin cross-arms in building the 
barbed-wire fence support because the arms were standard line 
equipment. It has been found cheaper, however, to employ 4-in. 
by 4-in. (10.16-cm. by 10.16-cm.) timbers. Square posts were 
selected for sightliness Building a small gate within the larger 



318 ELECTRICAL AIDS TO GREATER PRODUCTION 

one makes for convenience under ordinary operating conditions 
and also at times when equipment must be moved in or out. The 
same special dead-end fittings are used on this structure as on 
the two-pole type. The cost of this station without transformers 
and without the separate high-tension switching structure is 
$1,788. The costs are itemized in Table XL. 

TABLE XLI— BILL OF MATERIALS— FOUR-POUE STATION 

POLE STRUCTURE 

Item Quantity 

1 30-ft. poles 4 

-i 4-in. by G-in. hard pine 10 

17 2^-in. by 2 1 i -in. by ^s-in. square washer 70 

18 3 4-in. by 18-in. galvanized bolts 10 

20 -Vin. by 14-in. "ey e " bolts 6 

31 ^-itt- 0y S-ft. anchor rods 2 

32 Shim plates -1 

33 Three-bolt clamp 4 

34 a s-in. guy cable, ft 75 

FOUNDATIONS. ETC. 

12 Portland cement, bag 44 

13 Sand, cu. yd 4% 

14 Screened gravel, cu. yd 11 

10 Cinders, cu. yd 2 

FENCE 

2 14-ft. square posts 9 

3 4-in. by 4-in... 3%-ft yard post 13 

.5 Barbed wire, ft * 400 

20-in. cross-arm brace 13 

B Galvanized square-mesh fencing 96 

9 Gate 1 

15 io-in. by 4-in. lag bolts 13 

16 ^s-in. by iio-in. carriage bolts 13 

19 3 4 -in. by 14-in. galvanized bolts 13 

21 Staples * 5 

APPARATUS AND ACCESSORIES 

22 Ohio Brass strain disks 27 

23 Ohio Brass dead-end clamps 6 

24 Delta-Star type choke coil 3 

27 Delta-Star fuse mount No. B131 3 

28 Delta-Star disk switch, type 6 3 

29 West high ouse 200-kva,., 33,000-volt to 2300-volt transformer 3 

30 General Electric electrolytic arrester, type 1 1 

-in. by S-in. galvanized pipe 3 

1 1 Angle-iron hanger 3 

35 5 s-in. by 18-in. space bolts 4 

36 Ohio Brass insulation hooks 3 

37 2300-volt strain insulator 6 

38 S. C, No. 51 9 



OUTDOOR SUBSTATIONS 319 

Placed outside both, of these types of station about one span 
distant is a two-pole high-tension switch structure. The de- 
tached location for this structure was chosen to afford plenty of 
clearance for working on the station dead. The bill of material 
for this structure without apparatus is given in Table XLTII. 
The apparatus used in addition to that itemized list consists of 
a Burke disconnecting switch with separate cast pins. This 
latter feature is an improvement which makes it possible to 
change insulators without taking the switch down. It also does 
away with handling small parts which linemen are apt to drop 

TABLE XLII— COST OF SWITCH STRUCTURE 

Item Quantity 

Material $224 

Labor 50 

Superintendence 5 

Interest and miscellaneous contingencies 15 

Freight and drayage 25 

Ten per cent overhead 31 

Five per cent engineering and purchasing charges 18 

Total $368 

BILL OF MATERIALS— TWO-POLE SWITCH STRUCTURE 

Item Quantity 

1 Straight cedar poles 2 

2 4-in. by 6-in. by 16-ft. hard pine (long-leaf) 6 

3 4-in. by 4-in. by 16-ft. hard pine (long-leaf) 1 

4 Standard two-pin cross-arms 4 

5 2-in. by 4-in. by 4-ft. hard pine 25 

6 1-in. half-round single groove molding, ft 12 

7 %-in. by 20-in. spacing bolts 3 

8 26-in. standard cross-arm brace 8 

9 %-in. by 18-in. galvanized bolts 8 

10 %-in. by 12-in. galvanized bolts 8 

11 2*4-in. by 2%-in. by %6-in. square washers 56 

12 %-in. by 4%-in. carriage bolts 8 

13 %-in. by 4-in. lag screws 4 

14 20-d wire nails, lb 4 

15 1-in. pipe straps 4 

16 8-d wire nails, lb 1/6 

17 Ohio Brass dead-end clamp No. 6233 6 

18 Ohio Brass strain disk No. 11,535 18 

19 Dead-end angles 3 

20 %-in. by 9-ft. galvanized-iron pipe 1 

21 Ohio Brass hooks 6 

22 No. 2 B. & S. gage copper wire, ft 50 

23 Galvanized pole steps 11 



320 ELECTRICAL AIDS TO GREATER PRODUCTION 

and lose. The cost of this structure, including the switch, 
amounts to $368. The cost is itemized in Table XLII. 

TABLE XLIII— BILL OF MATERIALS— TWO-POLE STRUCTURE 

Item Quantity 

1 Straight cedar poles 2 

2 Schweitzer & Conrad or Burke sphere-gap arrester 3 

3 Standard 4-ft. cross-arm 4 

4 26-in. cross-arm braces 8 

5 Victor insulator No. 2335A or Ohio Brass No. 4535 9 

6 Ohio Brass clamps No. 6233 3 

7 %-in. by 18-in. spacing bolts 3 

8 Delta-Star type G choke coil 3 

9 Delta-Star type G fuse mount 3 

10 Transformers 3 

11 4-in. by 6-in. by 12-ft. hard pine 9 

12 Thomas insulator No. 3058 or Locke No. 3512 2 

13 Electric Service Supplies Co. iron pin No. 163 2 

14 %-in. by 18-in. galvanized bolts 4 

15 Locke or Ohio Brass attachments 3 

16 Locke or Ohio Brass attachments 3 

17 %-in. by 4^-in. carriage bolts 8 

18 y 2 -in. by 4-in. lag bolts 4 

19 Portland cement, bag 27 

20 Sand, cu. yd 2 

21 Screened gravel 5 

22 Three-bolt guy clamp 4 

23 Guy thimbles 4 

24 6-in. anchor rods 2 

25 3-in. by 3-in. anchor washers 2 

26 %-in. galvanized guy cable, ft 75 

27 Ground molding, ft 24 

28 1-in. pipe straps 12 

29 Upper ground cable, ft 40 

30 %-in. by 8-ft. ground pipe 1 

31 No. 2 B. & S. gage solid copper wire, ft 60 

32 i/^-in. by 7-in. machine bolts 18 

33 2%-in. by 2 1 / 4-in. square washers 42 

34 Schweitzer & Conrad No. 51A 3 

35 Washers placed under each through-bolt head and nut. 

The stations of these types which the company has built are 
proving satisfactory. Practically the only important change in 
the first design consisted of employing strain-type insulators on 
the poles near the lightning arresters (Fig. 92) instead of the 
pin-type insulators which were first selected. 

The outdoor substations described here were designed under 
the direction of W. F. Corl, general superintendent of the South- 
ern Illinois Light & Power Company. 



OUTDOOR SUBSTATIONS 



321 



THE UTILIZATION OF PIPE FOR OUTDOOR BUS WORK 

Copper, brass and iron pipe is now being used extensively in 
high-tension parts of outdoor substations for buses and connec- 
tions, the great advantage of being able to support it on rigid 
insulators instead of by strain insulators being generally recog- 
nized, says M. M. Samuels. 

No strict rules can be made as to how far apart pipe-bus sup- 
ports should be. The exact spacing of insulators must be deter- 
mined in each individual case. For instance, where a conductor 
runs parallel to a steel member, as in Fig. 93, with the steel 



Pipe Conduc+O' 



-A Deflect/on 



*r- 



6 round 

Clearance 



Steel Support 




Pipe Conductor 



Steel Support 



Steel Support 



|A 



V 



Oround 



A ; Clearance AA\ 

% Pipe ConduC tonj LA 



.mhii, iimui_(A 



13 



~ ~ - — '~^~ Deflect inn * 

Figs. 93 to 96 — Ground Clearance with Busbars Strung Above, Below 
and Across Steel Support — Form of Terminal 

TABLE XLIV— DIMENSIONS OF FLATTENED COPPEK OK BRASS 

PIPE FOR TERMINAL 

Size of Pipe in Inches 



y 8 % % % % i 1% i% 



2y 2 



Standard iron-pipe • 
size: 

A 0.57 0.76 0.96 1.20 1.52 1.86 2.44 2.82 3.56 4.32 5.28 

B 0.12 0.17 0.18 0.22 0.23 0.24 0.29 0.30 0.31 0.38 0.44 

Extra heavy iron-pipe 
size: 

A 0.54 0.72 0.91 1.15 1.48 1.85 2.39 2.76 3.49 4.20 5.16 

B 0.20 0.25 0.25 0.30 0.31 0.35 0.39 0.41 0.44 0.56 0.61 

member underneath the conductor, a large sag will considerably 
decrease the ground clearance. Therefore insulators must be 





"fc*. 




1 


























1 1 






v»_ 




v. 


































■fc " 


- ^_ 




^ 




























T 4 


-> ■-, 




































L 


x„ 






N 






















3 C 














».. 


























S:< 


^^ 










^. 




















o w 

■be 




J 


^-c^ 


.., 








^ ■■ 






















rl 






~^ 










„ 


















■>"' 










■%*» 






















c 


i c 




u, - 






















> 










-t- 




. 




-; - 


. 








s; 










-. 








C=>i-^i 




rJ?- 








^ 


-, 






K 










X 
















-ij* - 












^. 








^j 


, 






\ 














J 


'*- 


— , 










^L _ 
















\ 












"3? '- 


- ^ 




~ 


■- 








x^ 


^„ 














, 










■7T • 


• 


-_ 








»., s 








«fc 


x 






kx 




\ 










■~=~--_ 






* 




». 




-L^ 










<- 






\n 




A 


\ 






*~~s 












~--^. 








v. 


v 




x 


v 















-1 




















' 








V 


^x 






f 
























* 






"■ 


^ s 






\ 




f\ 


\ 


( 


"JV" - 


-_.. 


■*■■ 


--.. 


















•« 




X 




N 


; 




\\\ 




*-K^"~" 


_ 


-- - 






" - 


_ 


















v 


x 


\ 




vl 








J ~ 


-- 


_ 


"* 


«.„ r 


~ - 
















x^ 


■> 




\\ 


ya 














~T~ 




'- - 


._ 


"- 










' 


\ 












••It 














-^ 


"" 




*• 


^ 








\ 


\ 






,f 




















^ 


^ 


s 








\ Iwi 




<u 


























"^ 


x«, 


V 




X 1 






•§» 


5; 


























- 


X* 


" 




-M 






<; 
































^ 


\^ V 




6 


>; 


i 
I 
































V 


%A 




•^ 


^ 


































V\l 




\n 


J 


































a 






1 


































i 




1-1 


~_]^ 





































+- s 



in 



J 




3n 
































l 






"III 




V£- 


^ 
















































-x 










































4> > 

> a 

.2 a) 
+- a 




~ 


r 










""•^ 




















































>^ 


































-cxT~ 
-J— 


=»- 














s >. 
































^ 
















*•« 


j, 


































•-. 


, 












■ v 






































~ 






























~" 


'- 


.^ 


























s 
















— u 








* 


■"•-._ 












*^ 












^ 


































>. 


*> 








\ 


























"- 1 


-. 












» v 








■n 






1 






T~ 


~ 




















»., 










^ 






\ 












i 


3- 


i 






"~ 


^ 
















- . 






^ 
















*: 


J- 




, 








k ^ 


ir 














"<• 








s 






i 








j^ 










^ 










*- 


"> 








'^ v - 


V 






sN 




r^ 


k \ 






,2 


T 


J^ 












~ 










•5 










^H 






s \ 




\ 
































~^ 








^ 






s . 




\\ 


\ 






H 






























^ 


*«, ^_ 




*5 
















1 


='--. 




































>» 




V S 






pr 




S\ 




-i. 




j 


















*! 












^ v 








^ 


vv\ 


















=<, 


ij; 


- 






















\ 


-. 








\A 




N 


^ 




















*» 




_ 


-y 
















X 






SI 












- 


- 




















ftj. 














^r 




^wv\ 




















~ 


- 


~. 














^ 


g 










v\ 


Vk\VM 














Jb 


















~> 


» 










^ 


^^ 










.81 


































■» . 














n. 






































"~^^ 






"^ 


\VW 


Q 










































v x 






^vNv'l 


& 










































N 




UX 












1 f 






































v 


\B 


















































YK 


















































k v 














1 1 




































1 



9 



■g 
























































y 
















































o <" 
c 

— in 


"i-^ 


k 
















































r 








«. 








































■ 












•■« 




































>k 


















































- 

^ 




. 


















- 


























c 








^_ 


■- 


_ 




































J, 


. 
















r^ 
















s ^ 






















^ 
















c 


,-. 












x 










c 


i cc 


.f' 


_i> 










;- 


» 














^ 










^>^ 
















K~ 


















-^ 


-„ 












-< 


k ^ 






X 
















> 






- 


~. 


















-. 










<^ 


.J 
















fS; 


- 
















"~ 












<; 


^ 






"X- 


, 




s \ 










"p 








- : =- 












* 


-■ 


^ 


















- N 




K 








V 






























■~ 


^" 








s> 






s^ 


> 








V, 




































- 








\ 


X. 




w 






























































\\ 




r 




~r 


































^> 


** 




L * 


^> 




~\ 


^ 


P 


rt 




> 








~ 


- 




































X^ 




"\\ 




TO" 




_ 














































s 






1 














- 


__ 














~^ 




"^ 








s 


^~ 




X 


• s 


SSiAA- 


§ 






















~ 




- 


_. 










- 


i; 














<< 


































~ 




- _^ 


























































- 














pi 














































"" 






x i\\ a 


' 


















































W) 














































































































"Si 



J 


























































T 
















































\D O ' 








^ 














































;u. 








S.I 
















































> 




■# 














«. 


































CLLJ 






*1^ 




















.«, 




































- 


„ 
















h ^ 
























o 


OJ 
















~ 
















■"» 


























*A" 




















•>. 


^ 










k x 






























^ 














- 


», 










k ^ 












•+- 






















- 
































QCQ 


























"■ 


-~ 












v 
























-i?- 




■- 




r^ 




















-^ 










~"v 




















.-&■ 


~ 












- 


£"i 


















> 












\ 






















K - 


- 








"■ 




r> 














V 










\ 




























~ 


•-- 


^ 






■ ~ 


>~ 










k x 






X 




V 








Ki — 


























~- 


--. 






tj " 


5~^ 








k 




o 


oS 






jii'v 
















- 


















^. 














^CA? 






^ 


p^. 




















^_ 














~- 














A 


































— ; 


^; 


-^ 








A^ 








3Sl 






-- 


_ 


































<; 


, 






V 




















*~ 


- 




























<^ 


^^ 




XX 




\ 


5U 
























"" 


- 




_ 










^^ 


, 






^_ 


X\^ 




































~~ 


~ 








"5 


*; 






\\ 




> 












































"T 1 






nJ^s; 




















































V, 




tr. 


















































^L 






















































| 


\^a 


1 




















































Ni 






•J) 



< 
Q 
t-! 

w 



q c X 



CO 

w 

p 
m 

m 

< 

Q 

02 

H 
(U 

M 

o 

PS 



Q 

< 

02 

02 
< 
PS 



- J 


















































/)aS 




















































DO. 

>■— i 




/'•" 
















































77" 








-^ 


















































^ 


































Jn 
















> 
































S^ 


- 


- 


















,, 


































- 
















x^ 






















jij 
















; 














; v 


















^ 




» 


















C~ 












■ v 














% 


S 










"* 


























*5 












_3 






Z^*- 
















._ 
















^ 


K. 






XX 


















t^r 


'-•i 




r 


— ■ 














^, 


»- 














X 




X; 


























~ 


c 
















^ 










,x 






N 
















c 






























, 








s ^ 












Big; 














-i 


^ 










- 










^. 


S* 






X- 




V 






























^ 




"■ 








s 


i; 


. r 5 






A 
































jf 






- 






<s Xv 


\N 






















-- 


^ 












^ 


■S 






x; 














































•^J 


s^. 


r^- 


















































N N. ^s. \. V 






- 


— 1 






















~^~ 












•■ 


OT^vE 




















- 


- 
















^^- 






1\ 


\\'\\\ 


a" 
6 




























~- 


-1 


- 










^^^ 












































")-. 




^^ 












































-f. 




"xx 
















































x 
















































X \ 












































f 




1 PA^I 








































1 




1 1 rti 



,? ^= 



o 

■-0 



I s 
















































10 


1 




















































— 






-rrj- 


. 






















































"" 


- 










































xJlXj'- 
















^ 


















































" 


"■- 


, 




























c i^m 




■~ 


~. 


















v 
























C10 


^_i 








* 


» 








































tXi, 


















- 


, 












• N 




















- 


^ 














' 












N 


















^ 












~- 


























x 






























■ 


- 










% 








V 


•_'' 


















-J^-r 


- 
























». 


















X 














-T- 






— 




""- 


^T- 
















- 










X 






X 












? $~*— 


\- -) 


_ 








~ 
























r> 






\ 










.1 














~ 


~ 


-. 








•5 


;> 










v 






ix^ 11 


X 




\\ 








^ 


~ 




















- 


-.-, 




" 


*l 


^ 








x - 














i?w 














_ 




C 




. 












^~- 


^ 




^s 






-* 


s 








i^iTr 


























^ 


- 










X, 




s ^1 


x* 


\ 


NN:^ 




-I 


































^ 














X 


\N w 




-1^- 




"- 




- J 


















~+ 














^ 






s 




v !" 




I 


















- 


- 














*5 


5 






x. 




"N, 


X ? 




A\ 




ex. 

<4J 




























~ 












»4 


&1 




xx 






























1 












-- 


^ 






*. 




















































x 






XX, 


> 


















































x 






























































xO 






















































1 


























1 


1 






















\i 



PS 

w 

Ph 

P- 

o 
o 

o 

O 

H 
O 
W 



E % 



Ci 

6 



ssqouj ui uo\jfdd\pQ 



SSLjOUJ Ul UOI-j-DSIJ-aj] 



322 



OUTDOOR SUBSTATIONS 323 

spaced so that even with a maximum sag under ice conditions 
there will still be enough clearance between the conductor and 
the steel. But even for an individual case like this no rule can 
be made as to the minimum spacing of insulators, since the 
ground clearance at maximum sag will depend upon the insu- 
lator's height. 

When the conductor is suspended underneath the insulator 
with the steel above the conductor, as in Fig. 94, or when the 
conductor runs at right angles to the insulator, as in Fig. 95, a 
greater sag and consequently a greater distance between sup- 
ports is permissible. In this connection it may be mentioned 
that the majority of standard insulator pins on the market at 
present are too short to allow for the required ground clearance 
when used as in Fig. 93, since most standard pins are designed 
for cross-arm use as in Fig. 95. Caution should be used 
therefore when deciding upon the type of pin for a high-tension 
bus support. 

The curves in Fig. 97 give the deflection of the various 
kinds of pipe for different spacings of insulators, both without 
ice load and with ice load. They may be used readily for deter- 
mining the required spacing of insulators after a certain kind of 
pipe has been decided upon or to determine the size of pipe to 
be used when the distance between supports is fixed through 
other determinations. The deflections given are for two end 
supports and are therefore maximum. For a continuous pipe 
with more than two supports the deflections will be considerably 
less than those given. 

The simplest method of connecting a pipe connector to a ter- 
minal is to flatten the pipe, drill a hole through it, and use the 
pipe conductor itself as a terminal lug. 



INDEX 



Adapting 220-volt circuits to 110- 
volt lamps, 242 

Advantages and method of inter- 
locking motors, 176 

Advantages of electrified rolling 
mills, 161 

Advantages of wood duct for under- 
ground systems, 94 

Air gaps, motor, and allowable 
bearing wear, 189 

Alarms for hand-operated circuit 
breakers, 74 

Alarms for electrically operated cir- 
cuit breakers, 76 

Alarms, bell, 74 

Allowable sizes of wire for inter- 
mittent loads, 81 

Annealing furnaces, pyrometer sys- 
tems for, 279 

Applications of electricity, indus- 
trial, 1 

Applications of electric power, in- 
dustrial, 114 

Applying motors, considerations 
necessary in, 167 

Arc furnaces, 262 

Arc welder, characteristics of, alter- 
nating current, 281 

Arc welders, comparative character- 
istics of, 281 

Armature repair work, home-made 
tools for, 194 

Artificial daylight in the industries, 
200 

Automatic guard for drill presses, 
145 

Auxiliary switches and relays, 
weaknesses of, 72 



B 



Balking of induction motors, causes 

of, 190 
Ball bearings reduce maintenance, 

154 



Bearing wear, motor air gaps and 

allowable, 189 
Bearings, motor, should receive 

more attention, 188 
Bell alarms, 74 
Bending conduit, two methods of, 

111 
Blower and compressor service', 174 
Brass, results of tests on, 271 
Breakdown, suggested procedure in 

case of, 34 
Breakdown tests, 94 
Burn-outs, testing for, 56 
Bushings need close attention, 48 
Bus work, utilization of pipe for 

outdoor, 321 
Busbars, wall entrance for use with 

flat, 110 



C 



Cable, duct splicing saves short 
lengths of, 92 

Cable, tapping a 13,200-volt three- 
conductor, 112 

Card record system, 179 

Carrying overloads by increasing 
primary voltage, 102 

Cause of trouble with single-phase 
starter, 191 

Causes of the balking of induction 
motors, 190 

Causes of the jerky notching of 
motors, 190 

Causes of poor power factor, 39 

Changing horizontal motor to verti- 
cal in emergency, 192 

Choosing lighting units for indus- 
trial plants, 236 

Circuit breakers, electrically oper- 
ated, 76 

Circuit breakers, hand-operated, 74 

Circuits, adapting 220-volt to 110- 
volt lamps, 242 

Cleaning of transformers and detec- 
tion of flaws, 54 

Clutches, use of, 115 



325 



326 



INDEX 



Coils, device for winding, of any 
shape, 197 

Comments on actual installations, 
200 

Comparative characteristics of arc 
Avelders, 281 

Compressor service, blower and, 174 

Concurrent peaks, method of pre- 
venting, 178 

Conduction, transformation, switch- 
ing and protection, 47 

Conduit, two methods of bending, 
111 

Considerations necessary in apply- 
ing motors, 167 

Control, industrial motor, 134 

Control switches, types of desirable, 
58 

Convenient arrangement of fuses on 
feeder panels, 107 

Correction of power factor, 35 

Cost, actual installation, of inex- 
pensive switchboard, 104 

Cost, low over-all, and continuous 
production, 15 

Cost of factory lighting, 250 

Cost of inexpensive switchboard, 
actual installation, 104 

Cost of industrial switchboards, re- 
ducing the, 103 

Cost of outdoor substations, 314 
Crane areas, lighting, 251 
Cranes, power requirements for 
traveling, 173 



D 



Data on spot welding, 284 

Design, outdoor substation, 305 

Detection of flaws, cleaning trans- 
formers and, 54 

Determination of proper rating, 148 

Device for winding coils of any 
shape, 197 

Different size fuses, panel for test- 
ing, 109 

Disconnecting switches and instru- 
ment transformers, 64 

Distribution, effective, of factory 
power, 47 

Distribution transformers, testing 
the loads on, 299 

Dovetail glue jointer, 156 



Drill presses, automatic guard for, 
145 

Drive, conditions influencing, 146 

Drive, machine-tool, 138 

Drive, rolling mill, 161 

Drives, plate-shop, 146 

Duct, advantages of wood, for un- 
derground systems, 94 

Duct splicing saves short lengths of 
cable, 92 



E 



Economic measure, transformer in- 
spection, 48 
Economical loading of transformer 

banks, 96 
Economics, lighting, 211 
Economizing, use of light-weight 

motors a means of, 132 
Effect of lighting on accidents, 

spoilage and production, 208 
Efficient operation, 7 
Effective application of protective 

lighting, 225 
Effective distribution of factory 

power, 47 
Electric drive in the printing trade, 

172 
Electric drive, steam versus, 162 
Electric furnace for non-ferrous 

metallurgy (I, II, III), 253 
Electric furnaces, 5 
Electric furnaces, welding, etc., 253 
Electric heating versus other meth- 
ods, 289 
Electric melting, requirements of, 

257 
Electric power, industrial applica- 
tions of, 114 
Electricity, industrial applications 

of, 1* 
Electrified rolling mills, advantages 

of, 161 
Electrode cooling, 276 
Electrodes, properties and use of 

furnace, 274 
Elevator drive, factors that govern, 

173 
Emergency, changing horizontal mo- 
tor to vertical in, 192 
Emergency motor starting, trans- 
former connections for, 98 



1 



INDEX 



327 



Energy contract, selection of equip- 
ment depends on, 163 
Equipment, maintaining the, 223 
Equipment, maintenance of, 13 
Equipment, operation of, 12 
Equipment, installation and inspec- 
tion of, 11 
Equipment, selection of, 8 
Excessive speed in motor, large air 
gap cause of, 192 



Fuses, panel for testing different- 
size, 109 

Fuses, preventing installation of 
wrong-sized, 108 

Fuses, selection of, for induction 
motors, 106 

Flywheels are most desirable, ma- 
chines on which, 159 

Flywheels in woodworking, value 
of, 156 . 



Factors that affect selection, 150 

Factors that govern elevator drive, 
173 

Factory, improving motor drive in 
Maine shoe, 175 

Factory lighting, cost of, 250 

Factory lighting, standardizing, 216 

Factory power, effective distribution 
of, 47 

Factory wiring, how to avoid mov- 
ing, 252 

Feeder panels, convenient arrange- 
ment of fuses on, 107 

Feeder board, rebuilding a, without 
stopping service, 105 

Flat busbars, wall entrance for use 
with, 110 

Floodlighting versus distributed sys- 
tems, 156 

Flywheels, value of, in woodwork- 
ing, 229 

For and against synchronous mo- 
tors, 115 

Foundations, value of substantial, 
154 

From two- to three-phase with 
standard transformers, 100 

Furnace electrodes, properties and 
use of, 274 

Furnace, induction, 260 

Furnaces, arc, 262 

Furnaces, electric, 5 

Furnaces, electric, types of, 259 

Furnaces in commercial use, 268 

Furnaces, leads for, 277 

Furnaces, pyrometer system for an- 
nealing, 279 

Fuse rack, 182 

Fuses, convenient arrangement of, 
on feeder panels, 107 



G 



Graphic meters, 291-292 

Grinder drive, minimizing load with 
group, 143 

Grounding practice, prevailing trend 
in, 90 

Group and individual drive, power 
factor with, 28 

Group drive was advisable, where, 
153 

Group versus individual drive, 138 

Grounds, method of making sec- 
ondary, 91 

Guard for drill presses, automatic, 
145 



F± 



Handling material in industrial 
plants with electric tractors, 
300-304 

Hand-operated circuit breakers, 
alarms for, 74 

Heat treating by electric means, 278 

Heating compound to right temper- 
ature, 49 

Heating, electric, versus other meth- 
ods, 289 

Heating, industrial, 4 

Home-made tools for armature re- 
pair work, 194 

How selection of equipment depends 
on energy contract, 163 

How to avoid moving factory wir- 
ing, 252 



Illumination intensities specified, 
219 






328 



INDEX 



Illumination — selection of equip- 
ment economic, and specific 
applications. 200 
Illumination, speeding up manu- 
facturing by improving, 205 
Improving motor drive in Maine 

shoe factory, 175 
Individual drive, value of, 138 
Individual drive, group versus, 138 
Induction motors, selection of fuses 

for, 106 
Induction motors, starting, 135 
Industrial applications of electric 

power, 114 
Industrial applications of electric- 
ity, 1 
Industrial lighting code, new, for 

Wisconsin, 217 
Industrial lighting, some phases of. 

247 
Industrial lighting svstems, upkeep 

of, 250 
Industrial heating, 4 
Industrial motor control, 134 
Industrial plants, choosing lighting 

for, 236 
Industries, artificial davlight in the, 

200 
Inexpensive switchboard, actual in- 
stallation cost of, 104 
Inspection and maintenance service. 

32 
Inspection and installation of equip- 
ment, 11 
Installation and maintenance, IS 
Inspection, transformer, as economic 

measure, 48 
Instrument transformers, discon- 
necting switches and, 64 
Interlocking control apparatus, pos- 
sibility and value of, 68 
Interlocking motors, advantages 

and method of, 176 
Intermittent loads, allowable sizes 

of wire for, 81 
Interpole mill motors versus non- 

interpole, 129 
Interruption of production, prevent- 
ing, 24 



Jointer, dovetail glue, 156 



Lagging power factor, 42 

Lamps, adapting 220-volt circuits to 

110-volt, 242 
Large air gap cause of excessive 

speed in motor, 192 
Large shops, power requirements of 

machines in, 142 
Layout, map of motor, 182 
Leads for furnaces, 277 
Leads, trouble with, 50 
Light-weight motors a means of 

economizing, use of, 132 
Lighting a loom room for overtime 

operation, 251 
Lighting code, new industrial for 

Wisconsin, 217 
Lighting, cost of factory, 250 
Lighting crane areas, 251 
Lighting economies. 211 
Lighting, effect of, on accidents, 

spoilage and production, 208 
Lighting, effective application of 

protective, 225 
Lighting, some phases of industrial, 

247 
Lighting, standardization of, can ex- 
pedite shipbuilding. 232 
Lighting, standardizing factory. 216 
Lighting systems, rating artificial, 

238 
Lighting systems, upkeep of indus- 
trial, 250 
Lighting units, choosing for indus- 
trial plants, 236 
Lighting, workshop, 248 
Load, minimizing, with group 

grinder drive, 143 
Loads, allowable sizes of wire for 

intermittent, 81 
Loads on distribution transformers. 

testing the. 299 
Locations for pilot lamps, best, 66 
Loom-motor switches, 171 
Loom-room, lighting,' for overtime 

operation, 251 
Low over-all cost and continuous 

production, 15 
Low power factor, waste from, 37 

M 

Machine-tool drive, 138 



INDEX 



329 



Machines, power requirements of, in 
large shops, 142 

Maintaining the equipment, 223 

Maintenance, ball bearings reduce, 
154 

Maintenance, installation and, 18 

Maintenance, methods that facili- 
tate prompt, 179 

Maintenance of equipment, 13 

Maintenance service, inspection and, 
32 

Manufacturing plant, power prob- 
lem of the, 6 

Map of motor layout, 182 

Melting, advantages of electric, 
255 

Metallurgy, electric furnace for non- 
ferrous, 253 

Meters and measurements as ap- 
plied to industries, 291 

Meter, uses of the graphic, 291 

Method of finding motor load, 295 

Method of making secondary 
grounds, 91 

Methods of making temporary mo- 
tor repairs, 183 

Method of preventing concurrent 
peaks, 178 

Method of testing meters at two 
power factors, 297 

Methods that facilitate prompt 
maintenance, 178 

Milling drive, rolling, 161 

Mill motors, interpole versus non- 
interpole, 129 

Mills, advantages of electrified roll- 
ing mills, 161 

Minimizing load with group 
grinder drive, 143 

Modern outdoor substation, 305 

Motor air gaps and allowable bear- 
ing wear, 189 

Motor bearings should receive more 
attention, 188 

Motor, changing horizontal to verti- 
cal in emergency, 192 

Motor control, industrial, 134 

Motor-data sheet, 181 

Motor drive, improving, in Maine 
shoe factory, 175 

Motor-driven planers, 142 

Motor, large air gap cause of exces- 
sive speed in, 192 



Motor load, simple method of find- 
ing, 206 

Motor repairs, method of making 
temporary, 183 

Motor troubles, how to correct, 183 

Motor speed, reversed phase causes 
subnormal, 186 

Motor starting, transformer connec- 
tions for emergency, 98 

Motors, advantages and method of 
interlocking, 176 

Motors, causes of the balking of in- 
duction, 190 

Motors, causes of the jerky notch- 
ing of, 190 

Motors, control, specific application, 
troubles and remedies, 114 

Motors, for and against synchro- 
nous, 115 

Motors, interpole mill, versus non- 
interpole, 129 

Motors in the textile industry, 170 

Motors, selection of fuses for induc- 
tion, 106 

Motors, speeding shopwork with 
automatic control, adjustable- 
speed, 137 

Motors, starting induction, 135 

Motors, switching arrangement for 
testing, 198 

Motors, use of light-weight, a means 
of economizing, 132 

Motors, what synchronous, can and 
cannot do, 121 



N 



New industrial lighting code for 

Wisconsin, 217 
Non-interpole, interpole mill motors 

versus, 129 
Notching of motors, causes of the 

jerky, 190 



O 



Oil, painting of cases and care of, 

53 
Operation of equipment, 12 
Operation, efficient, 7 
Operations, unity-poweT-f actor, 119 
Outdoor substations, 305 
Outdoor substations, cost of, 315 



330 



INDEX 



Painting of cases and care of oil, 53 

"Panel for testing different size fuses, 
109 

Panels, convenient arrangement of 
fuses on feeder, 107 

Peaks, method of preventing concur- 
rent, 178 

Phase, reversed, causes subnormal 
motor speed, 186 

Picture of waste from low power 
factor, 37 

Pilot lamps, best location for, 66 

Pipe, utilization of, for outdoor bus 
work, 321 

Planers, motor-driven, 142 

Plate-shop drive, 146 

Poor power factor, causes of, 39 

Potheads, special uses for, 109 

Power factor, lagging, 42 

Power factor with group and indi- 
vidual drive, 28 

Power factor, correction of, 44 

Power factor improvement, how to 
encourage, 46 

Power factor correction — an urgent 
necessity (I, II ) , 35 

Power needed in woodworking. 160 

Power problem of the manufactur- 
ing plants, 6 

Power requirements for traveling 
cranes, 173 

Power requirements of machines in 
large shops, 142 

Prevailing trend in grounding prac- 
tice, 90 

Preventing installation of wrong- 
sized fuses, 108 

Preventing interruption of produc- 
tion, 24 

Printing trade, electric drive in the, 
172 

Problems of the manufacturing 
plants, power, 6 

Problems, power, of industrial 
plants, 1 

Procedure when poor power factor 
is evident, 43 

Production, low over-all cost and 
continuous, 15 

Production, preventing interruption 
of, 24 



Prompt maintenance, methods that 

facilitate, 179 
Proper rating, determination of, 148 
Properties and use of furnace elec- 
trodes, 274 
Protecting main transformers, 70 
Purchasing motors, things to con- 
sider in, 15 
Pyrometer system for annealing fur- 
naces, 279 



R 



Rack, fuse, 182 

Rating artificial lighting svstems, 
238 

Rebuilding a feeder board without 
stopping service, 105 

Record card, transformer, 101 

Reduce maintenance, ball bearings, 
154 

Reducing the cost of industrial 
switchboards, 103 

Repair work, home-made tools for 
armature, 194 

Repairs, methods of making tem- 
porary motor, 183 

Resistance to short circuit, 95 

Reversed phase causes subnormal 
motor speed, 186 

Rivets, welds as a substitute for, 
288 

Rolling mill drive, 161 

Rolling mills, advantages of electri- 
fied, 161 

Rotor, rubbing of, will cause fre- 
quent trouble, 188 

Rubbing of rotor will cause frequent 
trouble, 188 



S 



Safe methods in circuit breaking, 80 

Safety features in switching instal- 
lations (I, II, III), 57 

Saves short lengths of cable, duct 
splicing, 92 

Scheme for inspecting transformer 
interiors, 102 

Searchlamp and flood lamp require- 
ments, 227 



INDEX 



331 



Selection of equipment, 8 

Selection of equipment depends on 
energy contract, 163 

Selection of fuses for induction mo- 
tors, 106 

Selection, some factors that affect, 
150 

Shapers, vertical shaft motors for, 
155 

Shipbuilding, standardization of 
lighting can expedite, 232 

Shoe factory, improving motor drive 
in Maine, 175 

Shopwork, speeding, with auto- 
matic-control, adjustable-speed 
motors, 137 

Short circuit, resistance to, 95 ■ 

Some phases of industrial lighting. 
247 

Special uses for potheads, 109 

Speed motors, adjustable, 137 

Speeding shopwork with automatic- 
control, adjustable-speed mo- 
tors, 137 

Speeding up manufacturing by im- 
proving illumination, 205 

Splice diameter minimized, 92 

Spot welding, data on, 285 

Spot welding used extensively, 3 

Standardization of lighting can ex- 
pedite shipbuilding, 232 

Standardizing factory lighting, 216 

Starter, cause of trouble with 
single-phase, 191 

Starting induction motors, 135 

Starting torque, the, 115 

Steam versus electric drive, 162 

Substations, cost of outdoor, 314 

Substation, modern outdoor, 304 

Substations, outdoor, 304 

Switchboard, actual installation 
cost of, inexpensive, 104 

Switchboards and bus compart- 
ments, 62 

Switchboards, reducing the cost of 
industrial, 103 

Switches, loom-motor, 171 

Switching arrangement for testing 
motors, 198 

Switching installations, safety fea- 
tures in ; 57 

Synchronous motors are adapted, 
uses to which, 122 



Synchronous motors, for and 

against, 115 
Synchronous motors cannot give, 

service that, 121 
Synchronous motors can and cannot 

do, what, 121 

T 

Tapping a 13,200-volt three-conduc- 
tor cable, 112 

Testing motors, switching arrange- 
ment for, 198 

Testing the loads on distribution 
transformers, 298 

Testing for burn-outs, 56 

Testing meters, method of, at two 
power factors, 297 

Tests, breakdown, 94 

Textile industry, motors in the, 170 

Three-conductor cable, tapping a 
13,200 volt, 112 

Torque, the starting, 115 

Tractors, electric, handling material 
with, 300 

Transformer banks, economical 
loading of, 96 

Transformer connections for emer- 
gency motor starting, 98 

Transformer inspection as economic 
measure, 48 

Transformer interiors, scheme for 
inspecting, 102 

Transformer record card, 101 

Transformers, from two- to three- 
phase with standard, 100 

Transformers, protecting main, 70 

Transformers, cleaning of, 54 

Traveling cranes, power require- 
ments of, 173 

Troubles and how to correct them, 
some motor, 183 

Trouble, rubbing of rotor will 
cause frequent, 188 

Trouble with leads, 50 

Trouble with single-phase starter, 
cause of, 191 

Two methods of bending conduit, 
111 

Typical examples of effects, 39 

U 

Underground systems, advantages 
of wood duct for, 94 



332 



INDEX 



Unity-power-factor operations, 119 

Upkeep of industrial lighting sys- 
tems, 250 

Use of light-weight motors a means 
of economizing, 132 

Utilization of pipe for outdoor bus 
work, 321 



Value of flywheels in woodworking, 
156 

Value of substantial foundations, 
154 

Vertical shaft motors for shapers, 
155 

Voltage, carrying overloads by in- 
creasing primary, 102 



W 



Wall entrance for use with flat bus- 
bars, 110 



Weaknesses of auxiliary switches 
and relays, 72 

Welders, comparative characteris- 
tics of arc, 281 

Welding used extensively, spot, 3 

Welding, data on spot, 284 

Welding, electric, 280 

Welds as a substitute for rivets, 288 

What synchronous motors can and 
cannot do, 121 

Whole community may be affected, 
35 

Wire, allowable sizes of, for inter- 
mittent loads, 81 

Wiring, factory, how to avoid mov- 
ing, 252 

Woodworking, 152 

Woodworking, power needed in, 160 

Woodworking, value of flywheels in, 
156 

Workshop lighting, 248 

Wrong-sized fuses, preventing in- 
stallation of, 108 



v£> 

































— 




1 





































1 






































































J 




I 


\ 




















1 








( 








-4 


\ 


► 












t; 



2 



Q 



oo 



v£> 























1 












\|_ 
































































































































"■"^. 


N 








s 












<0 










Is 


















o 

o 


>o 


























































711 


3A. 


<a 



i 

— /^- 



































































1 

O 
V) 








































































































































*? 











































































-+J £ 



o oo o o o oo o o o o o o 

O O O O vfl ^f C\Jv£> lO >J if) (M — 

<\J — — 



£ 



O O O O O o oo 
o o o o « o o 

\S Ifi ^ rfi CO — T 













































































o 










































































/ 








( 


s 








\ 


s 










\ 














I 










1 


\ 








< 




















\ 










\ 


\ 


























1 

















1 






































































































y. 

Or 

3 














































- 










) 

















































o o oo o o o o oo o o o o o 

•a- CJ O oo Vi> ■■d- CM — Jf> o IT> o ir> 
^ — CM Csl — — 



> 

p 

Q 

o 
o 






cd erf nd 

5a J£ '~ 

CD ^ ?J ._ 

cd cc o 

O H3 O 

co O cj ■+-> 

£ .S fc * & 

S c H 



S cd 
erf bp 



O ^ 

i-5 cd 

j-i a; 

cd -3 , w 

■+-> T 

O £ CD 



Fh 02 

° S 

3 cd 

R « oj 



S CD 
erf ^ 



£ 58 



§ 2 
.a -v 

erf qT 

r-f 02 

a 3 

9 o 



O T3 
O 5 



^2 «w 

02 ° 

CD 02 

(D ^ 
U 

^ s 

erf cd 

<~ o? 
O 

02 § 

erf <3 

Crf -+3 



CD ~ 

Si 

-t-3 C^ 

cS O 

CD •— ' 
^^ 

CD • ^ 

^2 

H ^ 
M 
a 

CD 



" ^ i 

5 5h f-i 

O 2 ~ 

§ ^ "a 

S o •-> 

CD g 

cc3 +J 

fl O O 
bQ >>"£ 

O ej cS 
^.§^ 

~ CD .5 

XJ • 02 
CD J-c 

J) o fi 

02 -JJ ^ 

« « ri 

° d OJ 

CD ^ "S 

-M U rS 

o „ 

cd" g to 

02 CD C 

a > " 

" -l Crf gj 

O £H C 

erf +s t3 

CD O 

T3 o 
Crf CD 

O rC I 

i — i +j 02 



■4-c 



rS CD 



IS ^ crf 

>» ? Ph 

!h fH ft 
CD CD ° 

> pS +3 

C3 C CD 




Repreesextative Daily Load Curves 

pea.; 1 ,!; ^^^i:LTCo^ 7 V^ &Te 2T^ h lT ?r pari r w f -°r ,oads and tend to *» the «*- °* 

a very Li,,, load factor; for iLLoe t he cottonseed Si wi ' P ln the 6Vening - Certain of the loads have 

Others, like the cotton gin have a poor Ld factor SJ «- oxygen-gas generator, ice-cream manufacturing and refrigeration. 

ent operaW-cora and tw,„e „*£ ^^AS^^StES ^notSe!' ^^ t,,0 " 8,1 *" «*? 



